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STANDARDS 


OF THE 

AMERICAN INSTITUTE OF 
ELECTRICAL ENGINEERS 



1921 Revision 


[Printed, April 1921] 

PRICE, $ 2.00 

Copyright 1921 By A IE. E. 


Published by 

THE AMERICAN INSTITUTE OF ELECTRICAL ENGINEERS 
33 West Thirty-ninth Street, New York 




11 


STANDARDS OF THE A. I. E. E. 



PREFACE TO 1921 EDITION 


PURPOSE OF THE STANDARDS OF THE AMERICAN 
INSTITUTE OF ELECTRICAL ENGINEERS 

In framing these standards the chief purpose has been to define 
the terms and conditions which characterize the rating and 
behavior of electrical apparatus, with special reference to the 
conditions of acceptance tests. 

It has not been the purpose of the standards to standardize the 
dimensions or details of construction of any apparatus, lest the 
progress of design should be hampered 

NOTE 

The Standards Committee takes this occasion to draw the attention 
of the membership to the value of suggestions based upon experience 
gained in the application of the Standards to general practise. 

Any suggestions looking toward improvement in the Standards should 
be communicated to the Secretary of the Institute for the guidance of 
the Standards Committee in the preparation of future editions. 


MAY 23 1921 



§)CI. A614489 


PREFACE 


Or 


iii 


c 

a* 

v>9 


DEVELOPMENT OF THE STANDARDS 

OF THE 

AMERICAN INSTITUTE OF ELECTRICAL ENGINEERS 

The A. I. E. E. recognized at an early date in the development of elec¬ 
trical engineering the importance of standardization of electrical apparatus 
and at a meeting of its members in January, 1898, there was an 
important discussion on the “The Standardization of Generators, Motors, 
and Transformers.” This resulted in the appointment of a Committee on 
Standardization, consisting of seven members representing qualifications 
and experience from designing, manufacturing, and operating standpoints. 
The report of this Committee on standardization was presented and ac¬ 
cepted at a meeting of the Institute in June, 1899, and the rules embodied 
became the authoritative basis of American practice. 

Experience gained in applications of the Standardization rules and further 
developments in electrical apparatus and methods showed the necessity 
of revision, and a committee was appointed which after consultation with 
manufacturing and operating engineers presented the first revised report 
on Standardization Rules of the A. I. E. E. in June, 1902. 

The next revision was undertaken by a committee of ten, which pre¬ 
sented its report in May, 1906. 

In September, 1906, a Standards Committee of eleven members was 
appointed for further revision, and its report was presented in June, 1907. 

The appreciation of the importance and value of standardization 
resulted in the formation of a Standing Committee, with the title of Stand¬ 
ards Committee of the A. I. E. E. This became effective in the Constitu¬ 
tion of June, 1907. The scope and amount of work has necessitated 
increasing the number of members from time to time to the present 
membership of 37, within which are a number of sub-committees special¬ 
izing on various subjects. 

The Standards Committee is appointed each year by the President of 
the Institute and the practise has been to reappoint a number of the pre¬ 
vious committee, so that it is practically a continuous operating body. 

The present Standards of the A. I. E. E. are therefore the result of over 
twenty-one years of work on standardization by the Institute, conducted 
by members actively engaged in the design, manufacture, operation, and 
specifying of electrical apparatus. These men have freely contributed 
their time and knowledge, and have conducted much experimental work 
for the purpose. The Standards record the best American practise and 
experience. 


IV 


STANDARDS OF THE A. I. E. E 


SCOPE OF THE 1921 REVISION 

This edition of the Standards has been completely revised in 
form. This was considered necessary in view both of certain 
intrinsic defects in the original form, and the increase in com¬ 
plexity due to this form not being adapted to receive the addi¬ 
tions which are made from year to year. Furthermore several 
changes in substance have been made and a few sections added. 


PREFACE 


v 


OTHER APPROVED STANDARDS 

The following resolution, adopted by the Standards Committee, 
was approved by the Board of Directors on April 14, 1916: 

“The Standards Committee, with the approval of the Board of Direc¬ 
tors, recommends the use of the following rules and standards as adopted 
by other societies. These have been formally presented to the Standards 
Committee by the societies concerned and are found not to be incompatible 
with the Standards of the American Institute of Electrical Engineers.” 


Standardization of Service Requirements for Motors, as printed 
in the 1915 report of the National Electric Light Association. 

Standardization of Sizes, Voltages and Taps for Transformers, as 
printed in the 1916 report of the Electrical Apparatus Committee of 
the National Electrical Light Association. 

Standard Specifications for Magnetic Tests of Iron and Steel, of the 
American Society for Testing Materials. 

Report of the Joint Rubber Insulation Committee, published in the 
April, 1917, Proceedings of the American Institute of Electrical Engi¬ 
neers. 

Accuracy Specifications in Sections IV and V of the Joint Meter Code 
of the Association of Edison Illuminating Companies and of the National 
Electric Light Association. 

Accuracy Specifications in Section II of Circular 56 of the Bureau 
of Standards entitled Standards for Electric Service. 

Report of the Boiler Code Committee of the American Society of 
Mechanical Engineers. 

Suggested Safety Rules for Installing and Using Electrical Equipment 
in Bituminous Coal Mines, issued as Technical Paper 138 by the Bureau 
of Mines. 



VI 


STANDARDS OF THE A. I. E. E 


COOPERATING SOCIETIES 

The following societies directly and through the committees named, 
have given helpful cooperation in the preparation of these Rules: 

American Society for Testing Materials, 

Committee B- 1. 

Association of Edison Illuminating Companies, 

Committee on Meters. 

Illuminating Engineering Society, 

Committee on Nomenclature and Standards. 

Electric Power Club. 

Committee on Engineering Recommendations ; Standardization Committee. 

National Electric Light Association 
Committee on Meters. 

Committee on Apparatus. 

Association of Railway Electrical Engineers 
Committee on Wires and Cables. 

American Electric Railway Engineering Association, 

Committees on Equipment and Distribution. 

Institute of Radio Engineers, 

Committee on Standardization. 

Society of Automotive Engineers, 

Standards Committeel 


Railway Signal Association. 


TABLE OF CONTENTS 


Preface Page 

Purpose of the Standards of the A. I. E. E. ii 

Development of the Standards of the A. I. E. E. iii 

Scope of the 1921 Revision. iv 

Other Approved Standards. v 

Cooperating Societies. vi 


CHAPTER I 

General Principles Upon Which the A. I. E. E. Standards 

are Based. 

Heating. 1 

Mechanical and Commutation Limitation. 6 

Wave Shape. 6 

Dielectric Strength and Insulation Resistance. 7 

Efficiency. 7 

Rating. 8 

CHAPTER II 
General Rules. 

Operation. 9 

Temperature Limits. 9 

Rating. 10 

General. 10 

Ambient Temperature of Reference and Altitude Correction. 10 

Kinds of Rating. 10 

Rating by Temperature Rise. 11 

Tests. 14 

Ambient Temperature. 14 

Machine Temperatures. 14 

Details of Testing Methods. 15 

Efficiency. 16 

Wave Shape. 17 

Tests of Dielectric Strength. 17 

Insulation Resistance. 23 

Regulation. 24 

Construction. 24 

Rating Plates. 24 

CHAPTER III 
General Definitions 

Definitions. 25 

General. 25 

Resistivity..... 25 

Apparatus. 25 

Kinds of Currents. 25 

Alternating Currents. 26 

Circuits and Phases. 29 

Loads. 29 

Machinery and Apparatus. 31 

Symbols and Abbreviations. 32 

Bibliography. 33 

vii 









































Vlll 


STANDARDS OF THE A. I . E. E. 


CHAPTER IV 

Standards for Rotating Machines. 

(Other Than Railway Motors, Railway Substation Machinery 
Carrying Traction Loads, and Automobile Propulsion Machines.) 

Definitions. 34 

General. 34 

Functional Classification of Rotating Electric Machines .... 34 

Constructional Classification of Rotating Electric Machines.. 36 

Speed Classification of Motors.. 37 

Classification of Rotating Electric Machines Relative to Their 

Degree of Enclosure. 37 

Classification of Alternating Current Commutator Motors. .. 38 

Classification by Phases of Energy Supply. 38 

“ “ Speed Characteristics. 39 

“ “ Excitation. 39 

“ “ Neutralization and Compensation. 39 

“ “ Energy Reception. 39 

Miscellaneous Definitions. 40 

Operation. 42 

Temperature Limits. 42 

Rating. 43 

Units in which Rating Shall be Expressed. 43 

Limitations Other Than Temperature Rise. 43 

Tests...... 44 

Ambient Temperature. 44 

Machine Temperatures. 44 

Efficiency. 45 

Wave Shape. 49 

Tests of Dielectric Strength. 50 

Regulation. 51 

Bibliography. 54 

CHAPTER V 

Standards For Electric Railways and For Automobile Propulsion 

Machines. 

Definitions.... 55 

General. 55 

Contact Rails. 55 

Trolley Wires. 55 

Operation. 57 

Temperature limits. 57 

Rating... 57 

Ratings of Railway Substation Machinery and Transformers.. 57 

Ratings of Railway Motors. 58 

Ratings of Automobile Propulsion Machine's,.. 59 

Ratings of Electric Locomotives. 59 

Tests. 59 

Efficiency.. 59 

Characteristic Curves of Railway Motors. 61 

Selection of Railway Motor for Specified Service. 62 

Construction. 64 

Bibliography. 64 

CHAPTER VI 

Standards For Transformers and Other Stationary Induction 

Apparatus. 

Definitions. 65 

Apparatus. 55 

Parts of Apparatus. 66 

Properties of Apparatus. 66 













































TABLE OF CONTENTS ix 


Rating. 67 

General. 67 

Ambient Temperature of Reference. 68 

Altitude Correction. 68 

Units in which Rating Shall be Expressed. 68 

Kinds of Rating. 68 

Rating by Temperature Rise. 68 

Tests. 68 

Ambient Temperature. 68 

Transformer Temperatures. 69 

Efficiency. 72 

Wave Shape. 72 

Tests of Dielectric Strength. 72 

Regulation. 74 

Construction. 75 

Rating Plates. 75 

Transformer Connections. 75 

General. 75 

Single-Phase Transformers. 76 

Three-Phase Transformers. 78 

Three-Phase to Six-Phase Transformers. 79 

Bibliography. 80 

CHAPTER VII 

Standards For Switching, Control and Protective Apparatus. 

Definitions. 82 

Devices. 82 

Characteristics of Devices. 84 

Parts of Devices.. . 85 

Properties of Devices. 85 

Operation. 85 

Temperature Limits. 85 

Rating. 86 

Expression of Rating. 86 

Tests. 86 

Heat Tests. 86 

Tests of Dielectric Strength. 86 

Tests of Lightning Arresters. 87 

Bibliography. 87 

CHAPTER VIII 

Standards for Meters, Instruments and Instrument Transformers. 

Definitions. 88 

Operation. 89 

Rating. 90 

Tests. 90 

Specification of Characteristics. 91 

Bibliography. 91 

CHAPTER IX 

Standards for Wires and Cables. 

Definitions. 92 

Annealed Copper Standard. 94 

Operation. 95 

Temperature Limits. 95 

Designation. 95 

















































X 


STANDARDS OF THE A. I. E. E. 


Tests. 

General.. 

Tests of Dielectric Strength. 

Insulation Resistance... 

Capacitance or Electrostatic Capacity.. . • • 

Construction. 

Stranding.. 

Bibliography. 

CHAPTER X 

Standards for Storage Batteries. 


96 

96 

96 

98 

99 
101 
101 
103 


Text not Adopted. 


CHAPTER XI 
Standards for Illumination. 


General. 106 

Surfaces and Media Modifying Luminous Flux. 108 

Illumination.. 109 

Illuminants. 110 

Lamp Accessories. 110 

Photometry. 110 


CHAPTER XII 

Standards for Telephony and Telegraphy. 


Definitions. 113 

Line Circuits. 113 

Circuit Constants and Characteristics. 115 

Exuivalent Circuits. 116 

Telephony.... 117 

Telegraphy. 123 


CHAPTER XIII 

Standards for Radio Communication. 


General 


126 


CHAPTER XIV 

Standards for Prime Movers and Generator Units. 


General... 130 

Bibliography. 131 


CHAPTER XV 

Standards for Transmission Lines and Distribution Lines 
General... 


CHAPTER XVI 132 

Miscellaneous Standards. 


Heating Devices 


133 




























TABLE OF CONTENTS xi 

LIST OF TABLES 

Table Page 

100 Methods of Temperature Measurement. 2 

101 Conventional Allowance fbr Method III. 3 

102 Classification of Insulating Materials. 3 

103 Limiting Observable Temperatures. 4 

104 Limiting Observable Temperature Rises. 5 

200 Limiting Observable Temperature Rises. 12 

201 Temperature Coefficients of Copper Resistance. 16 

202 Needle-Gap Spark-Over Voltages. 20 

203 Spherometer Specifications. 21 

204 Sphere-Gap Spark-Over Voltages.. 22 

205 Air Density Correction Factors for Sphere Gaps. 23 

206 Insulation Resistance of Machines Excluding Oil-Immersed 

Apparatus. 23 

301 Symbols and Abbreviations. 32 

401 Classification of Losses in Machinery. 45 

402 Losses in Electric Machines. 46 

403 Brush Contact Drop. 48 

501 Temperatures of Railway Motors in Continuous Service.... 57 

502 Stand Test Temperature Rises of Railway Motors. 58 

503 Losses in Axle Bearings and Single-Reduction Gearing of 

Railway Motors. 60 

504 Core Loss in D. C. Railway Motors at Various Loads. 61 

505 Approximate Losses in D. C. Railway Motors. 61 

601—Limiting Observable Temperatures and Temperature Rises 

for Transformers Using Class A Insulation. 67 

901 High Voltage Tests for Rubber Insulated Wires and Cables.. 97 

902 High Voltage Tests for Varnished Cambric or Impregnated 

Paper Insulated Cables. 98 

903 Proposed Standard Cables. 100 

904 Standard Stranding of Concentric-Lay Cables. 101 

905 Stranding of Flexible Cables. 102 

906 Thickness of Insulation, 30 to 40 per cent Hevea Rubber 

Compound. 103 

1100 Photometric Units and Abbreviations. Ill 

I. E. C. RULES FOR ELECTRICAL MACHINERY. 


























































































































. 






* 


✓ > 





































STANDARDS 


OF THE 

AMERICAN INSTITUTE OF ELECTRICAL ENGINEERS 


CHAPTER I 

GENERAL PRINCIPLES UPON WHICH THE A. I. E. E. 
STANDARDS ARE BASED 

(All temperatures in this and the following chapters are given 
in centigrade degrees.) 

HEATING 

1000 General Principles. —The General Principles by reference to 
which the ratings of electrical machines are fixed, so far as their 
heating is concerned, admit that the life of insulating materials 
depends upon the temperatures to which these materials are sub¬ 
jected. Taking, as a basis, the results of experience with machinery 
in practical service and the results of laboratory tests of various 
insulating materials, limiting “hottest-spot” temperatures have 
been established for various classes of insulation for purposes of 
standardization. Limiting “observable” temperatures are de¬ 
duced from these limiting “hottest-spot” temperatures by sub¬ 
tracting therefrom a specified number of degrees which, for purposes 
of standardization represents the margin fixed between the limiting 
hottest spot and the limiting observable temperatures. 

This margin may be designated as the “ conventional allowance .” 

1001 Methods of Temperature Measurement. —There are three funda¬ 
mental methods of temperature measurement, namely: 

1. The Thermometer Method. 

2. The Resistance Method, and, 

3. The Embedded-Detector Method. 

The General Principles stated in Section 1000 permit of the use of 
whichever method is best suited to the class of machine, or part 
thereof, to be tested, by introducing appropriate values for the 
limiting observable temperature by each method. All the values 
of the observable temperatures are based upon the “hottest-spot” 
limitation adopted for purposes of standardization for the class of 
insulation employed. 

1002 Methods of Temperature Measurement Defined. —These three 
fundamental methods of making temperature measurements are 
designated Methods 1, 2 and 3, and are defined as follows: 

1 



2 


STANDARDS OF THE A. I. E. E. 


TABLE 100 

Methods of Temperature Measurement 


Method 

Description of Method 

1 . 

Thermometer Method. 

This method consists in the measurement of the tempera¬ 
ture, by mercury or alcohol thermometers, by resistance 
thermometers, or by thermocouples, any of these 
instruments being applied to- the hottest accessible 
part of the completed machine. This method does 
not include the use of thermocouples or resistance 
coils embedded in the machine as described under 
Method No. 3. 

2. 

Resistance Method. 

This method consists in the measurement of the tempera¬ 
ture of windings by their increase in resistance. In the 
application of this method, thermometer measurements 
shall also be made whenever practicable without dis¬ 
assembling the machine* in order to increase the prob¬ 
ability of obtaining the highest observable temperature. 
The measurement indicating the higher temperature 
shall be taken as the “observable” temperature. 

3. 

Embedded Temperature-Detector Method. 

This method consists in the measurement of the tempera¬ 
ture by thermocouple or resistance temperature 
detectors, located as nearly as possible at the estimated 
hottest spot. When Method No. 3 is used, it shall, 
when required be checked by Method No. 2. The 
highest observable temperature obtained from the 
readings of the embedded detectors shall not exceed the 
values permitted by the Rules for Method 3, and the 
highest observable temperature obtained by Method 2 
shall not exceed the values permitted by the Rules for 
Method 2. 


*Note. As one of the few instances in which the thermometer check cannot be applied 
in Method II, the rotor of a turbo alternator may be cited. 

1003 Conventional Allowances for the Three Methods of Temperature 
Measurement.—The specified differences by which the “observable” 
temperatures shall, for purposes of standardization, be assumed to 
be lower than the “hottest spot” temperatures, (which may be 
designated the “Conventional Allowances”), are as follows: 


Method 1. 15°C 

“ 2 . 10°6 

“ 3.(See following table). 















GENERAL PRINCIPLES 


3 


TABLE 101 

Conventional Allowance for Method 3 


Method 3. 


For windings with two coil-sides per 
, slot with detectors between top and 
bottom coil-sides (and between coil- 
sides and core). 

5°C 

For windings with one coil-side per 
slot for 5000 volts or less, with detect¬ 
ors between coil-side and, core and 
between coil-side and wedge. 

10°C 

For windings with one qoil-side per 
slot for more than 5000 volts, with 
detectors between coil-side and core 
and between coil-side and wedge. 

10°C plus l°Cfor every kv. of 
terminal pressure of the 
machine above 5 kv. 


1004 Classification of Insulating Materials.—The insulations employed 
in Electrical Machinery are subdivided into three main classes, 
designated A, B and C and defined as follows: 


TABLE 102 

Classification of Insulating Materials 


Class 

Description of Material. 

A. 

Cotton, silk, paper and similar materials when so treated 
or impregnated as to increase the thermal limit, or 
when permanently immersed in oil; also enamelled wire. 

When these materials are not treated, impregnated, or 
immersed in oil, they , are not included in Class A. 

B. 

Mica, asbestos and other materials capable of resisting 
high temperatures, in which any Class A material or 
binder is used for structural purposes only, and may be 
destroyed without impairing the insulation or mechani¬ 
cal qualities of the insulation. (The word “impair” 
is used in the sense of causing any change which could 
disqualify the insulation for continuous service.) 

C. 

Materials capable of resisting higher temperatures than 
Class B, such as pure mica, porcelain, quartz, etc. 
























4 


STANDARDS OF THE A. I. E. E. 


1005* Limiting “Hottest Spot” Temperatures.—The limiting “hottest 
spot” temperatures are, for purposes of standardization, taken at 
the following values: 

For Class A material.105°C (See Note 1) 

For Class B material.125°C (See Note 2) 

For Class C material.no limit yet specified. 

If different insulating materials are used on various parts of one 
winding (for instance in the slot and for the end windings) the temper¬ 
ature of each material shall not exceed the limit set for that material. 

When insulation consists of layers of materials having different 
temperature-limits (for instance high-temperature limit material 
adjacent to the copper and lower-temperature limit material adjacent 
to the iron or to the air) the temperature of each material shall not 
exceed the limit set for that material. 

1006 Limiting Observable Temperatures.—The limiting observable 
temperatures for use with methods 1, 2 and 3, are arrived at by 
subtracting the “conventional allowances” from the limiting 
“hottest-spot” temperatures for insulating materials. They are 
set forth as follows: 


TABLE 103 

Limiting Observable Temperatures 




Class A 
Material 

Class B* 
Material 

Method 1 


90° C. 

110° C. 

Method 2 

i 

95° C. 

115° C. 

Method 3 

For windings with 
two coil-sides per 
slot with detectors 
between top and 
bottom coil-sides 
and between coil- 
sides and core. 

100° C. 

120° C. 

For windings with 
one coil-side per 
slot with detectors 
between coil-side 
and core and be¬ 
tween coil-side and 
wedge. 

9 5° C. (minus 
1 degree for 
every 1000 
volts of term¬ 
inal pressure of 
the machine 
above5000 
volts). 

115° C. (minus 
1 degree for 
every 1000 
volts of term¬ 
inal pressure of 
the machine 
above5000 
volts). 


*See also note 2 Section 1005. 


(1005) Note 1. For cotton, silk, paper and similar materials when neither treated, im¬ 
pregnated nor immersed in oil, the limits of observable temperature and temperature rise 
shall be 15°C below the limits fixed for these materials when impregnated, 

(1005) Note 2. The Institute recognizes the ability of manufacturers to employ Class 
B insulation successfully at maximum temperatures of 150°C or even higher. However, as 
sufficient data covering experience over a period of years at such temperatures are at 
present unavailable, the Institute adopts 125°C as a conservative limit for this class of 
insulation, and any increase above this figure should be the subject of special guarantee 
by the manufacturer. 















GENERAL PRINCIPLES 


5 


1007 Limiting Observable Temperature of Oil. —The oil in which 
apparatus is permanently immersed, shall, in no part, have a temp¬ 
erature, observable by thermometer, in excess of 90°C. 

1008 Standard Ambient Temperatures of Reference. —The following 
values are adopted for the standard ambient temperatures of 


reference: 

For Air.40° C 

For Water.25°C 


These values for the standard ambient temperatures of reference 
apply to all conditions where the actual ambient temperature does 
not exceed them. 

The limiting observable temperature rise must not be increased 
even when the ambient temperature is lower than the standard 
ambient temperature of reference. 


1009 Limiting Observable Temperature Rises. —The limiting observ¬ 
able temperature rises in the following table 104 are obtained by 
subtracting the standard ambient temperatures of reference given 
in §1008 from the limiting observable temperatures given in Table 
103. The limiting observable temperature rises to be used in prac¬ 
tise are given later in the Rules. They are in some cases greater 
and in other cases smaller than those given in Table 104. See §1010 


TABLE 104 

Limiting Observable Temperature Rises 




Air Cooled 



Class A 

Class B* 

Method 1 


50°C 

70°C 

Method 2 


55°C 

75°C 

Method 3 

For windings with two 
coil-sides per slot, 
with detectors be¬ 
tween top and bottom 
coil-sides and between 
coil-sides and core. 

60°C 

80°C 

For windings with one 
coil-side per slot with 
detectors between coil- 
side and core and be¬ 
tween coil-side and 
wedge. 

55°C 

( minus 1 
degree for 
every 1000 
volts of 

t e rm ina 1 
pressure of 
the mach¬ 
ine above 
5000 volts). 

75°C 

( minus 1 
degree for 
every 1000 
volts of 

te rm in a 1 
pressure of 
the mach¬ 
ine above 
5000 volts). 


♦See also Note 2, Section 1005 


















6 


STANDARDS OF THE A. I. E. E. 


1010 General Comments on Special and Specific Cases.^— In the fore¬ 
going it has been assumed for the purpose of presenting a compre¬ 
hensive, logical and consistent plan, that the Rules actually used in 
the industry are exactly in accord with the General Principles. 
Practical experience indicates the necessity of establishing definite 
Rules to cover Special as well as Specific Cases. These Cases are 
set forth in later chapters. Any Case not specifically dealt with 
may come under the General Principles. 

1011 Comments on the Method of Measurement to be Employed.-^-In 

the absence of definite Rules, the manufacturer may, on the occasion 
of the acceptance test, use any of the three methods for the temper¬ 
ature measurements. In most cases, however, restrictions on the 
choice of method are imposed. These are set forth in the Rules. 

1012 Comments on Temperature Limits in Special Cases. —Tempera¬ 
ture limits are prescribed in the Rules for special cases where con¬ 
ditions determined by practice, by experience, or by agreements, 
require departures (often arbitrary)• from the limits of temperature 
rise corresponding to the General Principles. 

1013 Hottest Spot Temperature the Primary Point of Reference. —The 

hottest spot temperature is the primary point of reference, of 
the “bench-mark” used as the basis for the foregoing scheme or 
temperature delimitation. It is not employed in commercial trans¬ 
actions or in the ordinary course of testing or operation of electrical 
machinery. 

1014 Observable Temperature Rise the Working Standard. —The 

observable temperature rise is the working standard. A summary 
of working data with explanatory notes, will be found in Table 200. 

1016 Duration of Temperature Test and Correction to Time of Shut 
Down. —Whatever method of temperature measurement be em¬ 
ployed, it is required that 

(a) operation shall be continued until constant temperatures 
are determined if the machine has a continuous rating, or for the 
full period if the machine has a short time rating, and 

(b) when measurements cannot be made while the machine is 
loaded, appropriate corrections to raise the temperature readings 
to the time of shut down shall be applied. See Chap. II. 

MECHANICAL AND COMMUTATION LIMITATIONS. 

These limitations are set forth in subsequent Chapters dealing 
with specific kinds of machines. 

WAVE SHAPE. 

1200 The sine wave shall be considered as standard except where the 
departure therefrom is inherent in the operation of the system of 
which the machine forms a part. 


GENERAL PRINCIPLES 


7 


DIELECTRIC STRENGTH AND INSULATION RESISTANCE, 

(See §§2350 to 2380 incl.) 

1300 — The injury produced by dielectric stress applied to insulation 
is related to the time during which the stress is applied. A stress 
up to a certain limit may be applied for an indefinite period without 
injury to the insulation. A somewhat greater stress will cause 
heating of the insulation and a progressive deterioration, eventually 
resulting in breakdown. Higher values of stress cause more rapid 
deterioration and a quicker breakdown. It is customary to de¬ 
termine whether machinery will withstand the voltage stresses met 
in practice by a preliminary test for a definite period of time at a 
voltage considerably higher than the normal voltage to which the 
machinery is to be subjected, but not high enough to produce injury 
to the insulation during the period of test. 

1301— The test voltage which shall be applied to determine the suitability 
of insulation for commercial operation is dependent upon the kind 
and size of the machine, and its operating voltage, upon the nature 
of the service in which it is to be used, and upon the severity of the 
mechanical and electrical stresses to which it may be subjected. 
The voltages and other conditions of test which are recommended 
have been determined as reasonable and proper for the great majority 
of cases, and are proposed for general adoption, except when specific 
reasons make a modification desirable. 

1400 —The insulation resistance of machinery is of doubtful significance 
as compared with the dielectric strength. It is subject to wide 
variation with temperature, humidity and cleanliness of the parts. 
When the insulation resistance falls below prescribed values it 
can, in most cases of good design and where no defect exists, be 
brought up to the required standard by cleaning and drying the 
machine. The insulation resistance therefore may afford a useful 
indication as to whether the machine is in suitable condition for 
application of the dielectric test. 

EFFICIENCY 

(See §§2331 to 2333 incl.) 

1500 The conditions under which efficiency is determined are those 
normal to the operation of the machine. These include voltage, 
current, power factor, frequency, wave shape, speed, temperature, 
or such of them as may apply in each particular case. 

1501 The efficiency at all loads of all apparatus shall be corrected to a 
reference temperature of 75°C. 

1502 In the case of machinery, 'two efficiencies are recognized, con¬ 
ventional efficiency (§3524) and directly measured efficiency. Unless 
otherwise specified, the conventional efficiency is to be employed. 
When the efficiency of a machine is stated without specific reference 
to the load conditions rated load is always to be understood, 
whether the efficiency be the conventional or directly measured 
efficiency. 


8 


STANDARDS OF THE A. I. E. E. 


RATING 

(See §§2202 to 2232 incl.) 

1600 Principle of Machine Rating.—(a )Rating by Temperature Rise : 
The principle upon which machine rating is based, so far as relates 
to thermal characteristics, has been stated in earlier sections. 

(b) Rating by Limitations Other Than Temperature Rise: In 
some machines, the rating is limited by other than thermal considera¬ 
tions. In such cases, the principle upon which machine rating is 
based is that the rated load applied continuously or for a stated 
period, shall not cause the various limitations specified in later 
chapters; e. g., §§4260-4262 inclusive, to be exceeded. The rating 
shall be based upon the capacity as limited by heating unless the 
capacity as limited by other characteristics, is less. 


GENERAL RULES 


9 


CHAPTER II. 

GENERAL RULES 

The expressions “machinery” and “machines” are here employed 
in a general sense, in order to obviate the constant repetition of the 
words “machinery or induction apparatus.” 

To ensure satisfactory results, electrical machinery should be 
specified to conform to the Institute Standards, in order that it 
shall comply in operation, with approved limitations in the following 
respects, so far as they are applicable. 

Operating temperature 
Mechanical strength 
Commutation 
Dielectric strength 
Insulation resistance 
Efficiency 
Power factor 
Wave shape 
Regulation 

OPERATION 
Temperature Limits 

2104 Permissible Temperatures with Insulations of More Than One 
Class. —(a) If different insulating materials are used on various 
parts of one winding (for instance in the slot and for the end windings) 
the temperature of each material shall not exceed the limit set for 
that material. 

(b) When insulation consists of layers of materials having different 
temperature limits (for instance high-temperature-limit material 
adjacent to the copper and lower-temperature-limit material ad¬ 
jacent to the iron or to the air) the temperature of each material 
shall not exceed the limit set for that material. 

2116 Temperatures of Metallic Parts of Machines.— (a) Parts 

Adjacent to Insulating Material : Metallic parts of machines in con¬ 
tact with or adjacent to any kind of insulation, shall not attain a 
temperature in excess of that allowed for the adjacent insulation. 

( b ) Parts not Adjacent to Insulating Material : All parts of ma¬ 
chines other than those covered by §2116 (a) may be operated at 
such temperatures as shall not be injurious in any other respect. 

2120. Protection against Short Circuit.—The Institute recognizes the 
self-destructibility, both mechanical and thermal, of certain sizes and 
types of machines, when subjected to severe short-circuits, and 
recommends that ample protection be provided in such cases, external 
to the machine if necessary. 


10 


STANDARDS OF THE A. I. E. E. 


RATING 

General 

2202 Expression of Rating. —Except where otherwise specified the 
machines shall be rated in terms of their available output. For 
exceptions see §§4223, 5203, 6204 and 6223. 

2204 Institute Rating. —The Institute Rating of a machine shall be 
its rating when operating with a cooling medium of the ambient 
temperature of reference specified in §§2211 and 2212 and with 
barometric conditions within the range given in §2215. See 
§§2300, 2310, 2311, 4110 and 4300. 

Ambient Temperature of Reference and Altitude Correction 

2211 Ambient Temperature of Reference for Air. —The standard am¬ 
bient temperature of reference, when the cooling medium is air, shall 
be 40°C. 

2212 Ambient Temperature of Reference for Water-Cooled Ma¬ 
chinery. —-For water-cooled machinery, the standard temperature of 
reference for incoming cooling water shall be 25° C, measured at 
the intake of the machine. 

2213 Machines Cooled by Other Means. —Machines cooled by means 
other than air or water shall receive special consideration. 

2214 Outdoor Machinery Exposed to Sun’s Rays. —Outdoor machinery 
not protected from the sun’s rays at times of heavy load, shall receive 
special consideration. 

2215 Altitude. —Increased altitude has the effect of increasing the tem¬ 
perature rise of some types of machinery. In the absence of in¬ 
formation in regard to the height above sea level at which a machine 
is intended to work in ordinary service, this height is assumed not 
to exceed 1000 meters (3300 feet.) For machinery operating at an 
altitude of 1000 meters or less, a test at any altitude less than 1000 
meters is satisfactory, and no correction shall be applied to the ob¬ 
served temperatures. Machines intended for operation at higher 
altitudes shall be regarded as special. It is recommended that 
when a machine is intended for service at altitudes above 1000 
meters (3300 ft.) the permissible temperature rise at sea level, 
shall be reduced by 1 per cent for each 100 meters (330 ft.) by which 
the altitude exceeds 1000 meters. 


Kinds of Rating 

There are various kinds of rating such as: 

2220 Continuous Rating. —A machine rated for continuous service shall 
be able to operate continuously at its rated output, without exceeding 
any of the limitations established herein. 


GENERAL RULES 


11 


In the absence of any specification as to the kind of rating, the 
continuous rating shall be understood. 

2221 Short-Time Rating. —A machine rated for discontinuous or 
short-time service (i. e. service including runs alternating with stops 
of sufficient duration to ensure substantial cooling), shall be 
capable of operating at its rated output during a limited period, 
to be specified in each case, without exceeding any of the limitations 
established herein. Such a rating is a short-time rating. 

2222 Duty-Cycle Operation. —Many machines are operated on a cycle 
of duty which repeats itself with more or less regularity. For pur¬ 
poses of rating, either a continuous or a short-time equivalent load 
may be selected, which shall simulate as nearly as possible the 
thermal conditions of the actual duty-cycle. 

2223* Standard Short-Time Ratings. —The following periods shall be 
used for short-time ratings: 5, 10, 15, 30, 60 and 120 minutes. 

2224 A.I.E.E. and I. E. C. Ratings.—When the prescribed conditions of 
test are those of the A. I. E. E. Standards the rating of 
the machine is the Institute Rating. (See §2401) When 
the prescribed conditions of the test are those of the I. E. C. 
Rules, the rating of the machine is the I. E. C. rating. A 
machine so rated in either case may bear a distinctive sign upon its 
rating plate. I. E. C. stands for “International Electrotechnical 
Commission.” 

2225 Continuous Rating Implied. —Machines marked “A. I. E. E. 
Rating” or “I. E. C. Rating” shall be understood to have a contin¬ 
uous rating, unless otherwise marked in accordance with §§2223, 
5201 or 5202. 


Rating by Temperature Rise 

2230 Limiting Observable Temperature Rises. —The following 

limiting observable temperature rises have been adopted. 


(2223) When, for example, a short-time rating of 10 minutes duration is adopted, and 
the thermally equivalent load is 25 kw. for that period, then such a machine shall be stated 
to have a 10-minute rating of 25 kw. 

In every case the equivalent short-time test shall commence only when the windings and 
other parts of the machine are within 5° C. of the ambient temperature at the time of start - 
ing the test. 





12 


STANDARDS OF THE A. I. E. E. 


TABLE 200 

Limiting Observable Temperature rises for machines for operation 
in locations where the ambient temperature will not exceed 40°C. 
for Air or 26°C. for Water. 

For Class A insulation use the values in the Table 

For Class B insulation use 20 °C. higher values (or 45°C. higher in the cases 
covered by the Note in §1005). 

For Class C insulation no limits yet specified. 






Method 3 





For windings 

with two coil- 

For windings 



Method 

Method 

sides per slot 

with one coil- 



1 

2 

with detectors 

side per slot with 





between top and 

detectors against 





bottom coil-sides 

core and against 





and between coil 
sides and core. 

wedge. 


Items 










55°C. minusl°for 


• 




every 1000 volts 


1-Insulated windings 

50°C. 

55°C. 

60°C. 

by which the 


other than 2.3. 

Note 1 

Note 1 

Note 1 

terminal pressure 

C/3 

U 

Note 1 




of the machine 

4-> 

cd 





exceeds 5000 

CO 

c 

o 





volts). Note 1 

bo 

_c 

2-Single layer field 





nd 

G 

windings with ex- 





? 

posed surfaces un¬ 
insulated 

60°C. 

60°C. 

1 



3-Short circuited 






insulated windings 

60°C.. 





4-Field Windings 





C/3 

(other than 5.) 


55°C. 



o 

-t-> 

o 

5-Single layer field 






windings with ex- 

60°C. 

60°C. 



G 

O 

posed surfaces 





m 

bfl 

G 

uninsulated 





*3 

C 

• H 

£ 

6-Windings in slots 

50°C. 

55°C. 



7-Short-circuited 







insulated windings 

60°C. 





8-Transformers and 






Induction Regu¬ 
lators 

• 

55°C. 




Note 1—(a) The temperature of the windings of transformers and induction 
regulators is always to be ascertained by Method 2. 

(b) In measuring the temperature of air blast transformers, the air supply shall 
be shut off immediately at the end of the temperature run and air intake shall 






















































GENERAL RULES 


13 


be closed to prevent further admission of cooling air. In checking the temperatures 
ascertained by resistance, the readings of thermometers well distributed and in good 
contact with the coils shall be noted and the maximum temperature indicated by 
them, if higher than that determined by resistance, shall be taken as the maximum 
observable temperature of the windings. With the above procedure, the observable 
temperature rise for air-blast transformers may attain a value not in excess of 60°C. 
as determined by thermometer, although it must not exceed 55°C. as determined by 
resistance. 

(c) Method 3 shall be applied to all stators of machines with cores having a width 
50 cm. and over; it shall also be applied to all machines of 5000 volts and over if 
of over 500 kv-a. regardless of core width. 

(d) Method 2 shall not be used for circuits of low resistance (other than trans¬ 
former windings), such as interpole windings, where external joints and connections 
form a considerable part of the total resistance. 

(e) For all other cases it is optional to employ eitherMethod 1 or Method 2- 
(This is equivalent to authorizing Method 1 with a 5°C. lower limit of observable 
temperature than is permitted for Method 2). 

Note 2.—For cotton, silk, paper and similar materials when neither treated, im¬ 
pregnated nor immersed in oil, the limits of observable temperature rise shall be 15 
degrees below the limits in the above table fixed for these materials when impregnated # 

Note 3.—For enclosed machines (rotating) the limiting observable temperature 
rise shall be taken as 5 degrees higher than the values set forth in the Table for Items 
1 and 6. 

Note 4. A further limitation to this Table relates to the restriction of its applica¬ 
tion to machinery for operation in locations whose altitude is not more than 1000 
meters aftove sea level. Recommendations relating to the limiting temperature rise 
for machines for operation at higher altitudes are given in §§2215 and 2231. 

Note 5. If different insulating materials are used on various parts of one winding 
(for instance in the slot and for the end windings) the temperature of each material 
shall not exceed the limit set for that material. 

When insulation consists of layers of materials having different temperature* 
limits (for instance high-temperature limit material adjacent to the copper and lower 
temperature limit material adjacent to the iron or the air) the temperature of each 
material shall not exceed the limit set for that material. 

2231 Exceptions to Table 200. — (a) For cotton, silk, paper and 
similar materials when neither treated, impregnated nor immersed 
in oil, the limits of observable temperature rise shall be 15°C. 
below the limits fixed for these materials when impregnated. 

(b) When the thermometers are applied directly to the surfaces 
of bare windings, such as an edgewise strip conductor, or a cast 
copper winding, the limiting observable temperature rise shall be 
10°C. higher than given for Method 1 in the Table. 

(c) For commutators, collector rings, or bare metallic surfaces 
not forming part of a winding, the limiting observable temperature 
rise shall be 15°C. higher than given for Method 1 in the 
Table. 

(d) Any machinery destined for use with higher ambient temper¬ 
atures of cooling mediums, and also any machinery for operation at 
altitudes for which no provision is made in §2216, should be 
the subject of special guarantee by the manufacturer. The methods 
of test and performance set forth in these Rules, will, however, 
afford guidance in such cases. 

2232 Limiting Observable Temperature of Oil. —The oil in which 
apparatus is permanently immersed shall, in no part, have a tempera¬ 
ture, observable by thermometer, in excess of 90°C. 


14 


STANDARDS OF THE A. I. E. E. 


TESTS 

Ambient Temperature 

2300* Measurement of the Ambient Temperature During Tests of Ma¬ 
chinery. — (a) General: The ambient temperature is to be measured 
by means of several thermometers placed at different points around 
and half way up the machine at a distance of 1 to 2 meters (3 to 6 
feet), and protected from drafts, and abnormal heat radiation, 
preferablyas in §2301. 

( b) Mean Temperature: The value to be adopted for the ambient 
temperature during a test, is the mean of the readings of the ther¬ 
mometers (placed as above), taken at equal intervals of time during 
the last quarter of the duration of the test. 

( C) Use of Idle Unit: It is sometimes desirable to avoid errors due 
to time lag in temperature changes, by employing an idle unit of the 
same size and subjected to the same conditions of cooling as the unit 
under test, for obtaining the ambient temperature. 

2301 Oil Cup.—In order to avoid errors due to the time lag between the 
temperature of large machines and the variations in the ambient air, 
all reasonable precautions must be taken to reduce these variations and 
the errors arising therefrom. Thus, the thermometer for determining 
the ambient temperature shall be immersed in a suitable liquid, such 
as oil, in a suitably heavy metal cup. This can be made to respond to 
various rates of change, by proportioning the amount of oil to the 
metal in the containing cup. A convenient form for such an oil. cup 
consists of a massive metal cylinder, with a hole drilled partly through 
it. This hole is filled with oil and the thermometer is placed therein 
with its bulb well immersed. The larger the machine under test, the 
larger should be the metal cylinder employed as an oil Cup in the 
determination of the ambient ■ temperature. The smallest size’; 
of oil cup employed in any case shall consist of a metal cylinder 
25 mm. in diameter and 50 .mm. high (1 in. in diameter and 2 in. 
high). , 

Machine Temperatures 

2310 Temperature Rise for Any Ambient Temperature. —A machine 

may be tested at any convenient ambient temperature, preferably 
not below 10°C., but whatever be the value of this ambient tem¬ 
perature, the permissible rises of temperature musf not exceed those 
given in Table 200. 

2311 Correction for the Deviation of the Ambient Temperature of the 
Cooling Medium, at the Time of the Heat Test, from the Stand¬ 
ard Ambient Temperature of Reference.— Numerous experiments 
have shown that deviation of the temperature of the cooling medium 
from that of the standard of reference, at the time of the heat run, 
has a negligible effect upon the temperture rise of machines; there¬ 
fore, no correction shall be applied for this 1 deviation. ' 

(2300) The cpoling fluid ijiay either be led to the maphine through duct?, or through 
pipes, or merely surround the machine freely. In the former case the ambient temperature 
is to be measured at the intake of the machine itself. 



GENERAL RULES 


15 


2312 Duration of Temperature Test of Machine for Continuous Ser¬ 
vice. —The temperature test shall be continued until sufficient evi¬ 
dence is available to show that the maximum temperature and 
temperature rise would not exceed the requirements of the rules, 
should the test be prolonged until the attainment of a steady final 
temperature. 

2313 Duration of Temperature Test of Machine with a Short-Time 
Rating.— The duration of the temperature test of a machine with 
a short-time rating shall be the time required by the rating. In 
every case the equivalent short-time test shall commence only when 
the windings and other parts of the machine are within 5°C. of 
the ambient temperature at the time of starting the test. See §2235. 

2314 Duration of Temperature Test for Machine having more than 
One Rating. —The duration of the temperature test for a machine 
with more than one rating shall be the time required by that rating 
which produces the greatest temperature rise. In cases where this 
cannot be determined beforehand, the machine shall be tested sepa- 

• rately under each rating. 

2315 Temperature Measurements during Heat Run. —When possible 
temperature measurements shall be taken during operation, as 
well as when the machine is stopped. The highest figures thus 
obtained shall be adopted. In order to abridge the long heating 
period, in the ease of large machines, reasonable overloads of cur¬ 
rent during the preliminary period are suggested for them. 

2316 Rules for Correcting to Time of Shut-Down. —(a) Whenever a 
sufficient time has elapsed between the instant of shut-down and 
the time of the final temperature measurement to permit the temper¬ 
ature to fall, suitable corrections shall be applied, so as to obtain 
as nearly as - practicable the temperature at the instant of shut¬ 
down. This can sometimes be approximately effected by plotting 
a curve with temperature readings as ordinates and time as ab¬ 
scissas, and extrapolating back to the instant of shut-down. In 
other-instances, acceptable correction factors can be applied; e. g ., 
In the case of machines manufactured in large quantities, the 
correction obtained from tests made on representative machines 
may be used. 

(b) Exception. In cases where successive measurements show 
increasing temperatures after shut-down, the highest value shall 
be taken. 


Details of Testing Methods 

2320 Covering of Thermometer.—Thermometers used for taking 
temperatures of machinery shall be covered by felt pads 4 cm. 
x 5 cm. (134 in. x 2 in.), 3 mm. (3^ inch) thick cemented on; oil 
putty may be used for stationary and small apparatus. 


16 


STANDARDS OF THE A. I. E. E. 


2321 Temperature Coefficient of Copper. —The temperature coefficient 
of copper shall be deduced from the formula 1/(234.5 + t). Thus, 
at an initial temperature / = 40°C.,.the temperature coefficient of 
increase in resistance per degree centigrade rise is 1/(274.5 «= 
0.00364). The following table, deduced from the formula, is given 
for convenience of reference. 

TABLE 201 


Temperature Coefficients of Copper Resistance. 


Temperature of the winding, 
in degrees C. at which the 
initial resistance is measured. 

Increase in resistance of 
copper per °C., per ohm of 
initial resistance. 

0 

0.00427 

5 

0.00418 

10 

0.00409 

15 

0.00401 

20 

0.00393 

25 

0.00385 

30 

0.00378 

35 

0.00371 

40 

0.00364 


2322 Temperature Measurement of Low Resistance Circuit.—In 

circuits of low resistance, where joints and connections form a 
considerable part of the total resistance, the measurement of tem¬ 
perature by the resistance method shall not be used. (Except 
transformers, for which see §6320.) 

2323* Location of Embedded Temperature Detectors.—Embedded 
temperature detectors should be placed in at least two sets of 
locations. One of these should be between a coil-side and the 
core and one between the top and bottom coil-sides where two 
coil-sides per slot are used. Where only one coil-side per slot 
is used, one set of detectors shall be placed' between coil-side 
and core, and one set between coil-side and wedge. A liberal 
number of detectors shall be employed, and all reasonable 
efforts, consistent with safety, shall be made to locate them at the 
various places where the highest temperatures are likely to occur. 
See §1002. 

Efficiency 

2331* Efficiencies Recognized. —Two efficiencies are recognized, con¬ 
ventional efficiency and directly measured efficiency. Unless other- 

(2321) Temperature by Resistance: The temperature by resistance may be cal¬ 
culated by the following formula: 

Let 11 —■ resistance at t°C. 
rT = resistance at T°C. 

r T 

Then T - -(234.5 + 0 —234.5 

r f 

(2323) A coil side is one of the two active sides of the coil lying in a slot. 

(2331) The need for assigning conventional values to certain losses, arises from the 
fact that some of the losses in electrical machinery are practically indeterminable, and 
must, in many cases, either be approximated by an approved method of test, or else 
values recommended by the Institute and designated “conventional” values shall be em¬ 
ployed for themin arriving at the “conventional efficiency.” 







GENERAL RULES 


17 


wise specified, the conventional efficiency is to be employed See 

§§3514 and 3524. 

Input and output determinations of efficiency may be made 
directly, measuring the output by brake, or equivalent, where 
applicable. Within the limits of practical application, the circulating 
power method, sometimes described as the Hopkinson or “loading- 
back” method, may be used. 

2332* Normal Conditions for Efficiency Tests.— (a) General : The 
efficiency shall correspond to, or be corrected to, the normal con¬ 
ditions herein set forth, which shall be regarded as standard. These 
conditions include voltage, current, power-factor, frequency, wave¬ 
shape, speed, temperature, or such of them as may apply in each 
particular case. 

(b ) Load : When the efficiency of a machine is stated without 
specific reference to the load conditions, rated load is always to be 
understood whether t'he efficiency be the conventional or directly 
measured efficiency. 

( c ) Wave Shape : The sine wave, shall be standard, unless a different 
wave form is inherent in the operation of the system. See §2350. 

*(d) Temperature of Reference : The efficiency of all apparatus 
at all loads, shall be corrected to a reference temperature of 75° 
C, but tests may be made at any convenient ambient temperature, 
preferably not less than 15° C. 

(e) Poiver Factor : The efficiency of alternators and transformers 
shall be stated at the rated power factor. 

2333 Direct Measurement of Efficiency.— (a) General : Electric power 
shall be measured at the terminals of the apparatus. 

(b ) Polyphase Machines : In polyphase machines, sufficient 
measurements shall be made on all phases to avoid errors of unbalance. 

(c) Mechanical Power : Mechanical power delivered by machines 
shall be measured at the pulley, gearing or coupling, on the rotor 
shaft, thus excluding the loss of power in the belt or gear friction. 
See, however, an exception in §5202. 

Wave Shape. 

2340 Standard Wave Shape. —The Sine Wave shall be considered as 
standard, except where departure therefrom is inherent in the opera¬ 
tion of the system of which the electrical machine forms a part. 

Tests of Dielectric Strength 

\ 

2360 Condition of Machine to be Tested. —Commercial tests shall, 
in general, be made with the completely assembled machine and 
not with individual parts. The machine shall be in good condition, 
and high-voltage tests, unless otherwise specified, shall be applied 

(2332 d) In calculating plant or system efficiency it may be desirable to calculate the 
losses in each individual machine or part of the system at the actual temperature of 
that transformer or part during the specified interval. These losses may be appreciably 
different from the losses at 75° C, which latter shall be the standard temperature of reference 
for all efficiency guarantees. 





18 


STANDARDS OF THE A. I. E. E. 


before the machine is put into commercial service, and shall not 
be applied when the insulation resistance is low due to dirt or 
moisture. High voltage tests to determine whether specifications 
are fulfilled are admissible on new machines only. 

2361 Where High-Voltage Tests are to be Made. —Unless otherwise 
agreed upon, high-voltage tests of machines shall be made at the 
factory. 

2362 Temperature at which High-Voltage Tests are to be made.— 

High-voltage tests shall be made at the temperature assumed under 
normal operation or at the temperature attained under the con¬ 
ditions of commercial testing. 

2363 Points of Application of Voltage.— (a) General: The test volt¬ 
age shall be successively applied between each electric circuit and 
all other electric circuits and metal parts grounded. 

(6) Interconnected Polyphase Windings: Interconnected poly¬ 
phase windings shall be considered as one circuit. All windings ex¬ 
cept that under test shall be connected to ground. 

2364 Frequency and Wave Shape of Test Voltage. —The frequency 
of the testing voltage shall be not less than the rated frequency 
of the machine tested. A sine wave shape is recommended, (see 
§§2340 and 4361). The test shall be made with alternating voltage 
having a crest value equal to a/2 times the specified test voltage. 

2365 Duration of Application of Test Voltage. —(a) General : The 
testing voltage for machines shall be applied continuously for a 
period of 60 seconds. See exception §2365 (b). 

(b) Standard Machines and Devices produced in large quantities: 
Standard machines and devices produced in large quantities for 
which the standard test pressure is 2500 volts or less, may be tested 
for one second with a test pressure 20 per cent higher than the one 
minute test pressure. 

2356 Standard Test Voltage. —(a) General: The standard test volt, 
age for all machines, except as otherwise specified, shall be twice 
the normal voltage of the circuit to which the machine is connected 
plus 1000 volts. See exceptions §§2357, 4361, 6361. 

2357 Assembled Apparatus.—Where a number of pieces of apparatus 
are assembled together and tested as an electrical unit they shall 
be tested with 15 per cent lower voltage than the lowest required 
on any of the individual pieces of apparatus. 

2358 Measurement of Voltage in Dielectric Strength Tests. —There are 
two methods of measuring the voltage used in making dielectric 
strength tests, namely 

1. The voltmeter method. 

2. The spark gap method, using either the sphere spark gap or 
the needle spark gap. 

2369* Use of Voltmeters and Spark-gaps in Dielectric Tests.—When 

making high voltage tests on electrical machinery every precaution 

(2359) The resistance will damp high frequency oscillations at the time of breakdown 

and limit the resulting current. 

Carbon resistors should not be used because their resistance may become very low at 

high voltages. 



GENERAL RULES 


19 


must be taken against the occurrence of spark-gap discharges in 
the circuits from which the machine is being tested. A non-in¬ 
ductive resistance of about one ohm per volt of test pressure shall be 
inserted in series with one terminal of the spark gap. If the test is 
made with one electrode grounded, this resistance shall be inserted 
directly in series with the non-grounded electrode; if neither terminal 
is grounded one-half shall be inserted directly in series with each 
electrode. In either case this resistance shall be as near the measur¬ 
ing gap as possible and not in series with the tested apparatus. A 
water tube is the most suitable form of resistor. 

2360 Use of Spark-gap with Machines of Low Capacitance. —When the 
machine under test does not require sufficient charging current 
to distort the high-voltage wave shape, or change the ratio of trans¬ 
formation, the spark-gap should be set for the required test voltage 
and the testing apparatus adjusted to give a voltage at which this 
spark-gap just breaks down. This adjustment should be made 
with the machine under test disconnected. The machine should 
then be connected, and with the spark-gap about 20 per cent longer, 
the testing apparatus again adjusted to give the voltage of the 
former breakdown, which is the assumed voltage of test. This 
voltage shall be maintained for the required interval. 

2361* Use of Spark-gap with machines of High Capacitance. —When 
the charging current of the machine under test may appreciably 
distort the voltage wave or change the effective ratio of the testing 
transformer, the first adjustment of voltage with the gap set for 
the test voltage shall be made with the machine under test connected 
to the circuit and in parallel with the spark-gap. 

2362 Measurements with Voltmeter. —In measuring the voltage with 
a voltmeter, the instrument should preferably derive its voltage 
from the high-pressure circuit, either directly, or by means of a 
voltmeter coil placed in the testing transformer, or through an aux¬ 
iliary ratio transformer. It is permissible to measure the voltage 
at other places such as the transformer primary, provided corrections 
can be made for the variations in ratio caused by the charging 
current of the machine under test, or provided there is no material 
variation in this ratio. In any case when the capacitance of the 
machine to be tested is such as to cause wave distortion, the testing 
voltage must be checked by a spark gap as set forth in §§2364 and 2366 
or by a crest-voltage meter. If the crest-voltage meter is calibrated 
in crest volts, its readings must be reduced to the corresponding 
r. m. s. sinusoidal value by dividing by \/2 . 

(2361) When making arc-over tests of large insulators, leads, etc. partial arc-over of 
the tested apparatus may produce oscillations which will cause the measuring gap to dis¬ 
charge prematurely. The measured voltage will then appear too high. In such tests the 
“equivalent ratio” of the testing transformer should be measured by gap to within 20 per 
cent of the arc-over voltage of the tested apparatus with the tested apparatus in circuit. 
The measuring gap should then be greatly lengthened out and the voltage increased until the 
tested apparatus arcs over. This arc-over voltage should then be determined by multi¬ 
plying the voltmeter reading by the equivalent ratio found above. Direct measurement of 
the spark-over voltage over one gap by another gap should always be avoided. 



20 


STANDARDS OF THE A. I. E. E. 


2363 Measurements with Spark Gaps.—(a) General: If proper pre¬ 
cautions. are taken, spark gaps may be used to advantage in check¬ 
ing the calibration of voltmeters for high voltage tests of machines. 

(b) Range of Voltages : For the calibrating purposes set forth 
above the sphere gap shall be used for voltages above 50 kv., and 
is preferred down to 30 kv. The needle spark gap may, however, 
be used for voltages from 10 to 50 kv. 

2364 Needle Spark Gap.—The needle spark gap shall be between 
new sewing needles, supported axially at the ends of linear conductors, 
which are at least twice the length of the gap. There must be a 
clear space around the gap for a radius at least twice the gap length. 

2365 Needle Gap Sparking Distances.—The sparking distances in 
air between No. 00 double long sewing needle points for various 
root-mean-square sinusoidal voltages shall be assumed to be as 
shown in Table 202. 


TABLE 202 


Needle-Gap Spark-Over Voltages 

(At 25° C and 760 mm. barometer). 


R. M. S. Kilovolts 

Millimeters 

R. M. S. Kilovolts 

Millimeters 

10 

11.9 

35 

51 

15 

18.4 

40 

62 

20 

25.4 

45 

75 

25 

33 

50 

90 

30 

41 




The values in Table 202 refer to a relative humidity of 80 per cent. Variations 
from this humidity may involve appreciable variations in the sparking distance. 


2366* Sphere Spark-Gap.—The standard sphere spark gap shall be 
between two suitably mounted spheres. No extraneous body, or 
external part of the circuit, shall be nearer the spheres than 
twice their diameter. 

The shanks shall be not greater in diameter than Vsth.the sphere 
diameter. Metal collars etc., through which the shanks extend, 
shall be as small as practicable and shall not, during any measure¬ 
ment, come closer to the sphere than the maximum gap length 
used in the measurement. 

The sphere diameter should not vary more than 0.1 per cent, 
and the curvature, measured by a spherometer,, should not vary 
more than 1 per cent from that of a true sphere of the required 
diameter. 

(2366) When used as specified, the accuracy obtainable should be approximately 2 per 

cent. 










GENERAL RULES 


21 


2367* Use of Spherometer. —In using the spherometer to measure 
curvature, the distance between the points of contact of the sphero¬ 
meter feet shall be within the limits as indicated in Table 203. 


TABLE 203 

Spherometer Specifications 


Diameter of sphere 
in. mm. 

Distance between 

contact points in mm. 

Maximum 

Minimum 

62.5 

35 

25 

125 

45 

35 

250 

65 

45 

500 

100 

65 


2368 Sphere-Gap Sparking Distances. —The sparking distance be¬ 
tween spheres for various r. m. s. sinusoidal voltages shall be as¬ 
sumed to be as shown in Table 204. 

2369* Correction of Gap Spacing for Air-Density. —The spacing at which 
it is necessary to set a gap to spark over at some required volt¬ 
age, is found as follows. Divide the required voltage by the cor¬ 
rection factor given in Table 205 and use the new voltage thus 
obtained, to find the corresponding spacing from Table 204, using 
a graph of the latter, if more convenient. 

2370* Correction of Voltage for Air-Density. —The voltage at which a 
gap sparks over is derived from the voltage corresponding to the 
spacing in Table 204 by multiplying by the correction factor. 

(2367) In using sphere gaps constructed as indicated in §2366 and §2387, it is assumed 
that the apparatus will be set up for use in a space comparatively free from external dielec¬ 
tric fields. Care should be taken that conducting bodies forming part of the circuit, or at 
circuit potential, are not so located with reference to the gap that their dielectric fields are 
superposed on the gap, e. g., the protecting resistance should not be arranged so as to present 
large masses or surfaces near the gap, even at a distance of two sphere diameters. 

In case the sphere is grounded, the spark point of the grounded sphere should be approxi¬ 
mately five diameters above the floor or ground. 

(2369 and 2370) Effect of Air Density on Spark-Over Voltage. The spark-over volt¬ 
age, for a given gap, decreases with decreasing barometric pressure and increasing 
temperature. This variation may be considerable at high altitudes. When the variation 
from sea level is not great, the relative air density may be used as the correction factor; 
when the variation is great, or greater accuracy is desired, the correction factor corres¬ 
ponding to the relative air density should be taken from Table 204 in which 

0.392ft 

Relative air density = - 

273 -H 

ft = barometric pressure in mm. 

t = temperature in deg. C. 

Corrected curves may be plotted for any given altitude, if desired. It will be noted in 
Table 213 that for values of relative air density above 0.9 the correction factor does not 
differ greatly from the relative air density. 











22 


STANDARDS OF THE A. I. E. E. 


TABLE 204 

Sphere-Gap Spark-Over Voltages 


(At 25°C and 760 mm. barometric pressure) 



Sparking Distance in Millimeters. 

Kilo- 

62.5 mm. spheres 

125 mm. spheres 

250 mm. spheres 

500 mm. spheres 

volts 










One 

Both 

One 

Both 

One 

Both 

One 

Both 


sphere 

spheres 

sphere 

spheres 

sphere 

spheres 

sphere 

spheres 


grounded 

insulated 

grounded 

insulated 

grounded 

insulated 

grounded 

insulated 

10 

4.2 

4.2 







20 

8.6 

8.6 




.. . 



30 

14.1 

14.1 

14.1 

14.1 





40 

19.2 

19.2 

19.1 

19.1 





50 

25.5 

25.0 

24.4 

24.4 

. . 



. . 

60 

34.5 

32.0 

30. 

30. 

29 

29 



70 

46.0 

39.5 

36 

36 

35 

35 



80 

62.0 

49.0 

42 

42 

41 

41 

41 

41 

90 


60.5 

49 

49 

46 

45 

46 

45 

100 



56 

55 

52 

51 

52 

51 

120 



79.7 

71 

64 

63 

63 

62 

140 



108 

88 

78 

77 

74 

73 

160 



150 

110 

92 

90 

85 

83 

180 




138 

109 

106 

97 

95 

200 





128 

123 

108 

106 

220 





150 

141 

120 

117 

240 





177 

160 

133 

130 

260 





210 

180 

148 

144 

280 





250 

203 

163 

158 

300 






231 

177 

171 

320 






265 

194 

187 

340 







214 

204 

360 







234 

221 

380 







255 

239 

400 







276 

257 


The sphere gap is more sensitive than the needle gap to momentary rises of voltage 
and the voltage required to spark over the gap should be obtained by slowly closing 
the gap under constant voltage, or by slowly raising the voltage with a fixed setting 
of the gap. Open arcs should not be permitted in proximity to the gap during 
its operation, as they may affect its calibration. 


























GENERAL RULES 


23 


Table 205 


Air Density Correction Factors for Sphere Gaps. 


Relative 

air 

density 

Diameter of standard spheres in mm. 

62.5 

125 

250 

500 

0.50 

0.547 

0.535 

0.527 

0.519 

0.55 

0.594 

0.583 

0.575 

0.567 

0.60 

0.640 

0.630 

0.623 

0.615 

0.65 

0.686 

0.677 

0.670 

0.663 

0.70 

0.732 

0.724 

0.718 

0.711 

0.75 

0.777 

0.771 

0.766 

0.759 

0.80 

0.821 

0.816 

0.812 

0.807 

0.85 

0.866 

0.862 

0.859 

0.855 

0.90 

0.910 

0.908 

0.906 

0.904 

0.95 

0.956 

0.955 

0.954 

0.952 

1.00 

1.000 

1.000 

1.000 

1.000 

1.05 

1.044 

1.045 

1.046 

1.048 

1.10 

1.090 

1.092 

1.094 

1.096 


Insulation Resistance 

2380 General.—The insulation resistance test shall be made with all 
circuits of equal voltage above ground connected together. Circuits 
or groups of circuits of different voltage above ground shall be 
tested separately. 

2381 Voltage for Insulation Resistance Test.—Insulation resistance 
tests shall, if possible, be made at a d-c. pressure of 500 volts. Since 
the insulation resistance varies with the pressure, it is necessary 
that, if a pressure other than 500 volts is to be employed in any 
case, this other pressure shall be clearly specified. 

2382* Minimum Values.—The insulation resistance of a machine at its 


(2382) The order of magnitude obtained by this rule is shown in the following table 

TABLE 206 

Insulation Resistance of Machines Excluding Oil-Immersed Apparatus. 


Rated 
voltage 
of machine 

Megohms 

100 kv-a. 

1000 kv-a. 

10,000 kv-a. 

100 

0.091 

0.05 

— 

1,000 

0.91 

0.50 

0.091 

10,000 

9.1 

5.0 

0.91 

100,000 

— 

50 

9.1 
















24 


STANDARDS OF THE A. I. E. E. 


operating temperature shall be not less than that given by the 
following formula: 

voltage at terminals 

Insulation Resistance in megohms = -:-:—:-:———- 

rating m kv-a. + 1000 

The formula applies only to dry apparatus. Such high values are 
not attainable in oil-immersed apparatus. 

Regulation 

2390 Conditions for Tests of Regulation.—(a) Speed and Frequency: 
The regulation of generators shall be determined at constant speed, 
and that of alternating current machines at constant frequency. 

( b) Wave Form: A sine wave of voltage shall be assumed in de¬ 
termining the regulation of alternating current machinery receiving 
electric power, except where expressly specified otherwise. See 
§2340. 

(c) Temperature : It is desirable that all parts of the machine 
affecting the regulation be maintained at constant temperature be¬ 
tween the two loads and where the influence of temperature is of 
consequence, a reference temperature of 75° C. shall be considered 
as standard. If change of temperature should occur during the tests 
the results shall be corrected to the reference temperature of 75° C. 

CONSTRUCTION 
Rating Plates 

2401 Marking of Rating Plate.—(a) Distinctive Marking : It is recom¬ 
mended that the rating plate of machines which comply with the 
Institute Rules shall carry a distinctive special sign, such as “A.I.E.E. 
1920 Rating” or “A20” Rating. 

(b) Significance of Marking : The absence of any statement to 
the contrary on the rating plate of a machine implies that it is 
intended for continuous service and for the standard altitude and 
ambient temperature. See §§2211, 2212, 2215, and 2220. 

(c) Marking for Various Ratings : The rating plate of a machine 
intended to work under various kinds of rating must carry the 
necessary information in regard to those kinds of ratings. 



GENERAL DEFINITIONS 


25 


CHAPTER III. 

GENERAL DEFINITIONS 

In this chapter are given definitions which are of general application to 
electric circuits, machines and systems. Definitions pertaining to a 
specific class of apparatus are given in the chapter on the class of apparatus 
in question. The definitions here given are primarily descriptive rather 
than scientifically precise. 

The definitions given below for currents are also applicable, in most 
cases, to electromotive forces, potential differences, magnetic fluxes, etc. 

DEFINITIONS 

General 

3000 Ambient Temperature. —The ambient temperature is the tempera¬ 
ture of the air or water which comes into contact with the heated 
parts of a machine and carries off its heat. See §§2300 and 2301. 

Resistivity 

3020 Resistivity. —The resistivity of a material is the resistance ex¬ 
pressed in ohms between two opposite faces of a centimeter cube 
of the material, and is usually coupled with a statement of the tem- 
* perature. See §9050. 


Apparatus 

3064 Resistor. —A resistor is a device used primarily because it pos¬ 
sesses the property of electrical resistance. Resistors are used in 
electric circuits for purposes of operation, protection, or control. 

See §7018. 

3070 Inductor. —An inductor is a device used primarily because it 
possesses the property of inductance. 

3078 Reactor. —A reactor is a device used primarily because it pos¬ 
sesses the property of reactance. Reactors are used in electric 
circuits for purposes of operation, protection or control. 

Kinds of Currents 

3104 Direct Current. —A direct current is a unidirectional current. As 
ordinarily used, the term designates- a practically non-pulsating 
current. 

3108 Pulsating Current. —A pulsating current is a current which has 
regularly recurring variations in magnitude. As ordinarily em¬ 
ployed the term refers to a unidirectional current. 

3112 Continuous Current. —A continuous current is a practically non¬ 
pulsating direct current. 


26 


STANDARDS OF THE A. I. E. E. 


3116 Alternating Current.—An alternating current is a current the 
direction of which reverses at regularly recurring intervals. Unless 
distinctly otherwise specified, the term alternating current refers to a 
periodically varying current with successive half waves of the same 
shape and area. See §3212 

3120 Oscillating, or Free Alternating-Current.—An oscillating, or free 
alternating-current is the current following any electro-magnetic 
disturbance in a circuit having capacity, inductance, and less than 
the critical resistance. When the critical resistance of a circuit is 
reached the current becomes aperiodic. 

Alternating Currents 

3204 Cycle.—A cycle is one complete set of positive and negative 
values of an alternating current. 

3206 Period.—The period of an alternating current is the time required 
for the current to pass through one cycle. 

3208 Frequency.—The frequency of an alternating current is the 
number of cycles through which it passes per second, that is, the 
reciprocal of the period. 

3212 Wave Shape.—The wave shape, or wave form, of an alternating 
current is the shape of the curve obtained when the instantaneous 
values of the current are plotted against time in rectangular co¬ 
ordinates. 

Two alternating quantities are said to have the same wave shape 
when their ordinates of corresponding phase bear a constant ratio 
to each other. The wave shape, as thus understood, is therefore 
independent of the frequency of the current and of the scale to which 
the curve is plotted. 

3214 Sine-Wave, or Simple Alternating-Current.—^-A sine wave, or 
simple alternating-current is a current whose wave shape is sinusoidal. 

S218* Root-Mean-Square or Effective Value.—The root-mean-square 
or effective value of an alternating current is the square root of the 
mean of the squares of the instantaneous values for one complete 
cycle. It is usually abbreviated r. m. s. Unless otherwise speci¬ 
fied, the numerical value of an alternating current refers to its 
r. m. s. value. The word “virtual” is sometimes used in place of 
r. m. s., particularly in Great Britain. 

3222 Phase.—Phase is the fraction of the period of an alternating 
current which has elapsed since the current passed through the 
zero position of reference. 

This fraction is usually expressed in angular .measure, and the 
period corresponding to one complete cycle is taken as representing 
27T radians or 360 degrees. The angles are frequently called electric 
angles, and the degrees electric degrees. 

(3218) The r. m. s. value of a sine wave (see Section 3214) is equal to its maximum, or 

crest value, divided by V2. 



GENERAL DEFINITIONS 


27 


In the usual equation 

i = I m sin ( CO t + ip) 

the quantity ( CO t + ip) is the phase and ip is the phase angle of the 
current. 

3224* Phase Difference; Lead and Lag.—The phase difference of two 
alternating quantities of the same frequency is the difference be¬ 
tween their phases at any instant. That quantity whose maximum 
occurs first in time is said to lead the other, and the latter is said to 
lag behind the former. 

3228 Vector Representation and Angular Velocity.—A sine-wave current 
or voltage may be represented by a vector of constant length rotating 
counter-clockwise at a constant angular velocity (co = 2 7T /); 
this angular velocity is frequently termed the angular 
velocity of the current or voltage. 

3230* Counter-clockwise Convention.—It is recommended 
that, in any vector diagram, the leading vector be drawn 
counter-clockwise with respect to the lagging vector, as 
in Fig. 3—1 where 0 I represents the vector of a current 
in a simple alternating current circuit lagging behind the 0 
vector O E of impressed electromotive force. Fig. 3-1 

3234 Power.—Power is the rate of transfer of energy. In the case of 
an alternating-current circuit the word power is generally used to 
denote the average value of the power over a cycle. The power in 
an electric circuit at any instant is equal to the product of the values 
of the current and voltage at that instant, and is generally called the 
instantaneous power. 

3238 Apparent Power or Volt-amperes.—The apparent power, or volt- 
amperes, in an alternating current circuit is the product of the r. m. s . 
value of the voltage across the circuit by the r. m. s. value of the 
current in the circuit. Apparent power is also expressed in kilo¬ 
volt-amperes, abbreviated kv-a. 

3242* Power Factor.—Power factor is the ratio of the power to the 
apparent power. 

3246* Reactive Volt-amperes.—The reactive volt-amperes in a circuit is 
the square root of the difference between the square of the apparent 
power and the square of the power. 

3260* Reactive Factor.—The reactive factor is the ratio of the reactive 
volt-amperes to the total volt-amperes. 

(3224) When the two alternating quantities do not have the same wave form, the phase- 
difference as here defined may not be identical with equivalent phase-difference as defined 
in Section 3262. 

(3230) See Publication 12 of the International Electrotechnical Commission (Report of 
Turin meeting, Sept. 1911, p. 78.) 

(3242) The power factor when both the current and voltage are sinusoidal is equal to 
the cosine of the angle which expresses their difference in phase (see Section 3224). 

(3246) The reactive volt-amperes, when both current and voltage are sinusoidal, it 
equal to the volt-amperes times the sine of the angle which expresses the phase difference 
between current and voltage. 

S250) The reactive factor, when both current and voltage are sinusoidal, is equal to 
the sine of the angle which expresses their phase difference. 





28 


STANDARDS OF THE A. I. E. E. 


3254* Active Component.—The active component of the current in a 
circuit is the average power divided by the voltage. 

3256* Reactive Component.—The reactive component of the current 
in a circuit is the square root of the difference between the square 
of the current and the square of the active component of the current. 
3260 Equivalent Sine Wave.—An equivalent sine wave is a sine wave 
which has the same frequency and the same r. m. s. value as the 
actual wave. 

3262 Equivalent Phase Difference.—The equivalent phase difference 
(applicable to non-sinusoidal currents and voltages) is the phase 
difference between the equivalent sine waves of current and voltage 
when so related as to have the same power factor as the non-sinp- 
soidal quantities. 

There are cases, however, where this equivalent phase difference 
is misleading, since the presence of harmonics in the voltage wave, 
current wave, or in both, may reduce the power factor without 
producing a corresponding displacement of the two wave forms with 
respect to each other; e. g., the case of an a-c. arc. In such cases, 
the components of the equivalent sine waves, the equivalent reactive 
factor and the equivalent reactive volt-amperes may have no physical 
significance. 

3266* Crest Factor or Peak Factor.—The crest factor or peak factor of 
a wave is the ratio of the crest, or maximum, value to the r. m. s. 
value. 

3270* Form Factor of a Wave.—The form factor of a wave is the ratio of 
the r. m. s. to the algebraic mean ordinate taken over a half cycle be¬ 
ginning with the zero value. If the wave passes through zero more 
than twice during a single cycle, that zero shall be taken which gives 
the largest algebraic mean for the succeeding half-cycle. 

3274 Deviation Factor of a Wave. —The deviation factor of a wave is 
the ratio of the maximum difference between corresponding ordi¬ 
nates of the wave and of the equivalent sine wave to the maximum 
ordinate of the equivalent sine wave when the waves are superposed 
in such a way as to make this maximum difference as small as possible. 
3278 Telephone Interference Factor of a Wave. (See §4352)—The 
telephone interference factor is the ratio of the square root of the 
sum of the squares of the weighted values of all the sine wave 
components (including in alternating waves both fundamental and 
harmonics) to the r. m. s. value of the wave. 

(3254) The active, or in-phase component of the current in a circuit corresponds to 
average power passing in a given direction through the circuit. With sine wave voltage 
and current, the active component of the current is in phase with the voltage. 

(3256) The reactive, or quadrature, component of the current in a circuit correspond* 
to power alternating in direction in the circuit so that the average value of the power 
transferred in a given direction through a cycle is zero. With sine wave current and 
voltage the reactive component of the current is in quadrature with the voltage. 

(3266) The crest factor of a sine wave is V 2. 

IT 

(3270) The form factor of a sine wave is -=ror 1.11. 

2 V2 




GENERAL DEFINITIONS 


29 


Circuits and Phases 

3304 Electric Circuit. —An electric circuit is a path in which an electric 
current may flow. Strictly speaking, an electric circuit is a complete 
circulatory path, but the term circuit is commonly employed to 
designate a specific part of a complete path. When part of a com¬ 
plete path is referred to, such as a branch circuit, a derived circuit, 
or a conductor, both the terminals and the conductor which form 
that path should be specified in order to avoid ambiguity; e. g., 
the circuit a-b-c. When the whole circuit is referred to, it may be 
designated as a complete or closed circuit. 

3324* Single-Phase Circuit. —A single-phase circuit is a circuit ener 
gized by a single alternating electromotive force. 

3326* Three-Phase Circuit. —A three-phase circuit is a combination of 
circuits energized by alternating electromotive forces which differ 
in phase by one-third of a cycle; i. e., 120 degrees. 

3328* Quarter-Phase or Two-Phase Circuit. —A quarter-phase or two- 
phase circuit is a combination of circuits energized by alternating 
electromotive forces which differ in phase by a quarter of a cycle; 
i. e., 90 degrees. 

3330* Six-Phase Circuit. —A six-phase circuit is a combination of cir¬ 
cuits energized by alternating electromotive forces which differ in 
phase by one sixth of a cycle; i. e., 60 degrees. 

3332 Polyphase Circuit.—A polyphase circuit is a circuit of more than 
a single phase. This term is ordinarily applied to symmetrical 
systems. 

3344 Symmetrical Voltages and Currents. —Polyphase voltages or 
currents are symmetrical when the voltages or currents have the 
same wave shape and r. nr. s. value and differ in phase each from the 
next by the same angle. 

3348 Symmetrical Polyphase System. —A symmetrical polyphase 
system is a polyphase system in which the voltages are symmetri¬ 
cal. 

3352* Balanced Polyphase System. —A balanced polyphase system 
is a polyphase system in which both the currents and voltages are 
symmetrical. 

Loads 

3404 Reactive Load. —A reactive load is a load in which the current 
lags behind or leads the voltage across the load. 

(3324) A single-phase circuit is usually supplied through two wires. The currents in 
these two wires, counted outwards from the source, differ in phase by 180 degrees or 
a half cycle. 

(3326) In practise the phases may vary several degrees from the specified angle. 

(3328) In practise the phases may vary several degrees from the specified angle. 

(3330) In practise the phases may vary several degrees from the specified angle. 

(3352) The term balanced polyphase system is applied also to a quarter-phase (or two- 
phase) system in ivhich the voltages have the same wave form and r. m. s. value and in 
which the currents have the same wave form and r. m. s. value and differ in phase by ninety 
electrical degrees. 



30 


STANDARDS OF THE A. I. E. E. 


3406 Non-reactive Load.—A non-reactive load is a load in which the 
current is in phase with the voltage across the load. (The term 
non-inductive load is sometimes used for non-reactive load.) 

3408 Inductive Load.—An inductive load is a reactive load in which the 
current lags behind the voltage across the load. 

3410 Condensive Load.—A condensive load is a reactive load in which 
the current leads the voltage across the load. 

3414* Balanced Polyphase Load.—A balanced polyphase load is a 
load to which symmetrical currents are supplied when it is con¬ 
nected to a system having symmetrical voltages. 

3424 Connected Load.—The connected load on any system, or part of 
a system, is the combined continuous rating of all the receiving 
apparatus on consumers’ premises which is connected to the system, 
or part of the system under consideration. 

3434 Peak Power.—The peak power is the average power during a 
* time interval of specified duration occurring within a given period 
of. time, that interval being selected during which the average power 
is greatest. 

3438 Load Factor.—The load factor is the ratio of the average power to 
the peak power. 

In each case, the interval of maximum load and the period over 
which the average is taken should be definitely specified, such as 
a “half-hour monthly’’ load factor. The proper interval and period 
are usually dependent upon local conditions and upon the purpose 
for which the load factor is to be used. 

3442 Plant Factor.—The plant factor is the ratio of the average load 
to the rated capacity of the power plant; i. e., to the aggregate 
ratings of the generators. 

3464 Demand of an Installation or System.—The demand of an in¬ 
stallation or system is the load which is drawn from the source of 
supply at the receiving terminals averaged over a suitable and 
specified interval of time. Demand is expressed in kilowatts, 
kilovolt-amperes, amperes, or other suitable units. 

3468 Maximum Demand.—The maximum demand of an installation 
or system is the greatest of all the demands which have occurred 
during a given period. It is determined by measurement, according 
to specifications, over a prescribed time interval. 

3460 Demand Factor.—The demand factor of any system or part of 
a system, is the ratio of the maximum demand of the system, or 
part of a system, to the total connected load of the system, or of 
the part of the system under consideration. 

3464 Diversity Factor.—The diversity factor of any system, or part 
of a system, is the ratio of the sum of the maximum power demands 

(3414) The term balanced polyphase load is applied also to a load to which are supplied 

two currents having the same wave form and r. m. s. value and differing in phase by ninety 

electrical degrees when it is connected to a quarter-phase (or two-phase) system having 

voltages of the same wave form and r. m. s. value. 



GENERAL DEFINITIONS 


31 


of the subdivisions of the system, or part of a system, to the maximum 
demand of the whole system, or part of the system under considera¬ 
tion, measured at the point of supply. 

Machinery and Apparatus 

3504 Capacity (or Properly, Capability).—The word “capacity” is fre¬ 
quently used in the general sense of “capability”. It is also used 
in a more exact sense to denote the load which, when carried by a ma¬ 
chine, apparatus, or device will, under specified conditions of test, 
cause it to reach any one of its physical limitations , such for example, 
as operating temperature or ability to maintain required voltage. 

Capacity should be distinguished from rating. On account of the 
different senses in which it has been employed (see §3508), ca¬ 
pacity is less used than it formerly was, rating being more useful 
commercially. 

3508* Rating.—A rating of a machine, apparatus or device is an arbi¬ 
trary designation of an operating limit. 

(The rating of a machine is the output marked on the rating plate, and 
shall be based on, but shall not exceed the maximum load which can 
be taken from the machine under prescribed conditions of test. This 
is also called the rated output. Maximum possible rating obviously 
corresponds with capability as defined in §3504). 

3614 Efficiency.—The efficiency of an electric machine or apparatus 
is the ratio of its useful output to its total input. Unless otherwise 
specified the above output and input shall mean the power output 
and the power input respectively. 

3524* Conventional Efficiency.—The conventional efficiency of an 
electric machine or apparatus is the ratio of the output to the sum 
of the output and the losses, or of the input minus the losses to the 
input, when, in either case conventional values are assigned to one or 
more of these losses. 

3534 Plant, or System, Efficiency.—Plant, or system, efficiency is the 
ratio of the energy delivered from the plant or system to the energy 
received by it in a specified period of time. In calculating plant, or 
system, efficiency it may be desirable to calculate the losses, in each 
individual machine, or part of the system, at the actual temperature 
of that machine, or part, during the specified interval. These losses 
may be appreciably different from the losses at 75° C., which latter 
shall be the standard temperature of reference for all efficiency 
guarantees. This definition is not applicable to storage bat¬ 
teries. See §2332. 

3535 Regulation.—The regulation of a machine in regard to some 
characteristic quantity (such as terminal voltage or speed) is 

(3508) The term maximum load does not refer to loads applied solely for mechanical, 
commutation, or similar tests. 

(3524) The need for assigning conventional values to certain losses, arises from the fact 
that some of the losses in electric machinery are practically indeterminable, and must, in 
many cases, either be approximated by an approved method of test, or else values recom¬ 
mended by the Institute and designated “conventional” values shall be employed for them 
in arriving at the “conventional efficiency.’.’ 



32 


STANDARDS OF THE A. I. E. E 


the change in that quantity occurring between any two loads. 
Unless otherwise specified, the two loads considered shall be zero 
load and rated load, and at the temperature attained under normal 
operation. The regulation may be expressed by stating the numeri¬ 
cal values of the quantity at the two loads, or it may be expressed 
by the “percentage regulation”, which is the percentage ratio of 
the change in the quantity occurring between the two loads, to the 
value of the quantity at either one or the other load, taken as the 
normal value. The normal value may be either the no-load value, 
as the no-load speed of induction motors; or it may be the rated- 
load value, as in the voltage of a-c. generators. 

It is assumed that all parts of the machine affecting the regulation 
maintain constant temperature between the two loads, and where 
the influence of temperature is of consequence a reference temperature 
of 75° C. shall be considered as standard. 

TABLE 301. 

3604* SYMBOLS AND ABBREVIATIONS 


Symbol for Abbreviation 

Name of Quantity. the Quantity. Unit. for the Unit. 


Acceleration due to gravity g 

Admittance.... F, y 

Angular velocity. CO 

Capacitance (Electrostatic ) ^ 

capacity). J 

Conductance. g 

Conductivity. y 

Current. I,i 

Dielectric constant. K 

Efficiency. 7 ] 

Electromotive force, abbre¬ 
viated e. m. f. E, e 

Electrostatic field intensity F 

Electrostatic flux. T 

Electrostatic flux density. . D 

Energy, in general. U or W 

Frequency..... / 

Impedance. Z, z 

Inductance (or coefficient \ ^ 

of self induction). j 

Intensity of magnetization J 

Length. I 

Magnetic field intensity. . . H, 3C 

Magnetic flux.•. <F, (p 

Magnetic flux density. .... B, (B 


{ centimeter Cm. 

per second per sec. 

per second per sec. J 

mho .... 

radian per 
second 

farad .... 

mho .... 

*mho per cen- \ mho per 
timeter J cm. 
ampere ' .... 

per cent .... 

volt .... 


joule, watt-hour .... 

cycle per second — 

ohm .... 

henry .... 

centimeter cm. 

gilbert per gilbert per 

centimeter cm. 

or gauss* .... 

maxwell .... 

gauss .... 




















GENERAL DEFINITIONS 


33 


Magnetomotive force, ab¬ 
breviated m. m. f. 

Mass. m 

Mutual Inductance (or co¬ 
efficient of mutual induction) 
Number of conductors or ^ 


turns. 

Permeability.M = B/H 

Phase displacement. p 

Potential difference, abbre¬ 
viated p. d.. . .. V, v or E, e 

Power. / . P, P 

Quantity of electricity.... Q, q 

Reactance. X, x 

Reluctance... (ft 

Resistance. R, r 

Resistivity. p 


Standard acceleration due 

to gravity (at about 45 deg. go 
latitude and sea level) equals 


980.665*.. 

Susceptance. b 

Susceptibility. k = J/H 

Temperature. 6 

Time.. t 

Velocity of rotation. n 

Voltage. E, e or V, v 




gilbert* 


gram g 

henry 

/ convolution 
\ or turn of wire 


degree or 
radian 


volt 

watt 

coulomb, 

ampere-hour 

ohm 



ohm 

f * ohm-centi- 
[ meter 
centimeter 
per second 
per second 


ohm-cm. 



mho 


degree centigrade °C 
second sec. 

( revolution rev. per 
\ per second sec. 

volt .... 


3608 Symbols for Maximum, Instantaneous and R. M. S. Values.— 

E m , I m and P m should be used for maximum cyclic values, e, i and 
p for instantaneous values, E and I for r. m. s. values (see 
§3218) and P for the average value of the power, or the active power. 
These distinctions are not necessary in dealing with direct- 
current circuits. In print, vector quantities should be represented 
by boldface capitals. 

BIBLIOGRAPHY 

Associazione Elettrotecnica Italiana: Simboli e Notazioni. 
International Electrotechnical Commission: International Symbols. 


(3604) The gauss is provisionally accepted for the present as the name of both the 
unit of field intensity and flux density, on the assumption that permeability is a simple 
numeric. 

An aditional unit for magnetomotive force is the “ampere-turn”, for flux the “line”, 
for magnetic flux-density “maxwells per sq. in.”. 

The numerical values of resistivity and conductivity are ohms resistance and mhos con¬ 
ductance between two opposite faces of a cm. cube of the material in question,, but the 
correct names are as given, not ohms and mhos per cm, cube, as commonly stated 

The value 980.665 for go has been the accepted standard value for many years and was 
formerly considered to correspond accurately to 45° latitude and sea level. Later re¬ 
searches, however, have shown that the most reliable value for 45° and sea-level is slightly 
different: but this does not affect the standard value eiven above. 
























34 


STANDARDS OF THE A. I. E. E. 


CHAPTER IV. 

STANDARDS FOR ROTATING MACHINES (OTHER 
THAN RAILWAY MOTORS, RAILWAY SUBSTATION MA¬ 
CHINERY CARRYING TRACTION LOADS, AND AUTO¬ 
MOBILE PROPULSION MACHINES). 

The A. I. E. E. Standards for Rotating Machines are the General 
Standards shown in Chapters II and III and the Standards in other 
chapters which are applicable to the devices involved, together with the 
modifications and extensions given in this chapter. 

DEFINITIONS 

General. 

Certain rules applying exclusively to railway machinery have, for 
convenience, been placed in Chapter V, with cross references in 
all cases in this chapter. The rules of Chapter IV apply to railway 
machinery except as they are modified by rules of Chapter V. 

4000 Classification of Electric Rotating Machinery. —Rotating elec¬ 

tric machinery may be classified in various ways, these classi¬ 
fications over-lapping or interlocking in considerable degree. First, 
Rotating electric machinery may be classified as Direct- 
Current and Alternating-Current; Second, according to the 
function of the machines; e. g., Motors, Generators, Boosters, 
Motor-Generators, Dynamotors, Double-Current Generators, 
Converters and Phase Advancers; Third, according to con¬ 
struction or principle of operation; e . g., Commutating, 

Synchronous, Induction, Unipolar, Rectifying. Obviously, some 
of these machines could be rationally included in either classifica¬ 
tion, e. g., Motor-Generators and Rectifying Machines. 

In the following, self-evident definitions have for the most part 
been omitted. 

Functional Classification of Rotating Electric Machines. 

4001 Generator. —A generator is a machine which transforms mechani¬ 
cal power into electric power. 

4002 Motor. —A motor is a machine which transforms electric power 
into mechanical power. 

4003 Booster.—A booster is a generator inserted in series in a circuit 
to change its voltage. A booster may be driven by an electric 
motor (in which case it is termed a motor-booster) or otherwise. 

4004 Motor-Generator Set. —A motor-generator set is a transforming 
device consisting of one or more motors mechanically coupled to 
one or more generators. 


ROTATING MACHINES 


35 


4005 Dynamotor.—A dynamotor is a transforming device combining 
both motor and generator action in one magnetic field, either with 
two armatures, or with one armature having two separate windings 
and independent commutators. 

4005 Direct-Current Compensator or Balancer.—A direct current 
compensator or balancer is a machine which- comprises two or 
more similar direct-current machines (usually with shunt or com¬ 
pound excitation) directly coupled to each other and connected 
in series across the outer conductors of a multiple-wire system of 
distribution, for the purpose of maintaining the potentials of the 
intermediate wires of the system, which are connected to the junc¬ 
tion points between the machines. 

4007 Double-Current Generator.—A double-current generator is a 
machine which supplies both direct and alternating currents from 
the same armature-winding. 

4008 Converter.—A converter is a machine which employs mechanical 
rotation in changing electric energy from one form into another. 
There are several types of converters, as defined in §§ 4009 to 
4013 below. 

4009 Direct-Current Converter.—A direct-current converter is a machine 
which converts from a direct current to a direct current, usually 
with a change of voltage. Such a machine may be either a motor- 
generator set or a dynamotor. 

4010 Synchronous Converter.—A synchronous converter (sometimes 
called a rotary converter) is a machine which converts from an 
alternating to a direct current, or vice-versa. It is a synchronous 
machine with a single closed-coil armature winding, a commutator 
and slip rings. 

4011 Cascade Converter.—A cascade converter (also called a motor 
converter) is a combination of an induction motor with a synchronous 
converter, the secondary circuit of the former feeding directly into 
the armature of the latter; i. e., a synchronous converter concatenated 
with an induction motor. 

4012 Frequency Converter.—A frequency converter is a machine 
which converts the power of an alternating-current system from one 
frequency to another, with or without a change in the number of 
phases, or in the voltage. 

4013 Rotary Phase-Converter.—A rotary phase-converter is a machine 
which converts from an alternating-current system of one or more 
phases to an alternating-current system of a different number of 
phases, but of the same frequency. 

4014 Phase Advancer.—A phase advancer is a machine which supplies 
reactive volt-amperes to the system to which it is connected. Phase 
advancers may be either synchronous or asynchronous. 

4015 Synchronous Condenser or Synchronous Phase Advancer.— 

A synchronous condenser or synchronous phase advancer is a syn¬ 
chronous machine, running either idle or with load, the field ex- 


36 


STANDARDS OF THE A. I. E. E. 


citation of which may be varied so as to modify the power factor 
of the system, or through such modification to influence the load 
voltage. 

Constructional Classification of Rotating Electric Machines 

4016 Direct-Current Commutating Machines.—A direct current com¬ 

mutating machine comprises a magnetic field of constant polarity, 
an armature, and a commutator connected therewith. Specific 
types of direct-current commutating machines are: Direct-Current 
Generators; Direct-Current Motors; Direct-Current Boosters; 

Direct-Current Motor-Generator Sets and Dynamotors; Direct- 
Current Compensators or Balancers; and Arc Machines. 

4017 Alternating-Current Commutating Machine.—An alternating cur¬ 
rent commutating machine comprises a magnetic field of alternating 
polarity, an armature, and commutator connected therewith. 

See §§ 4071 to 4074. 

4018 Synchronous Commutating Machine.—Synchronous commutat¬ 
ing machines include synchronous converters, cascade-converters, 
and double-current generators. 

4019 Synchronous Machine.—A synchronous machine comprises 
a constant magnetic field and an armature receiving or delivering 
alternating-currents in synchronism with the motion of the machine; 
i. e., having a frequency strictly proportional to the speed of the 
machine. Specific types of synchronous machines are defined 
in §§ 4020 to 4023 below. 

4020 Alternator.—An alternator is a synchronous alternating-current 
generator, either single-phase or polyphase. 

4021 Polyphase Alternator.—A polyphase alternator is a polyphase 
synchronous alternating-current generator, as distinguished from a 
single-phase alternator. 

4022 Inductor Alternator.—An inductor alternator is an alternator 
in which both field and armature windings are stationary, and in 
which masses of iron or inductors, by moving past the coils, alter 
the magnetic flux through them. It may be either single-phase 
or polyphase. 

4023 Synchronous Motor.—A synchronous motor is a machine structur¬ 
ally identical with an alternator, but operated as a motor. 

4024 Induction Machine.—An induction machine is a machine wherein 
primary and secondary windings rotate with respect to each other; 
e. g., induction motors, induction generators, certain types of fre¬ 
quency converters and certain types of rotary phase-converters. 

4025 Induction Motor.—An induction motor is an alternating-cur- 
rent motor, either single-phase or polyphase, comprising independent 
primary and secondary windings, one of which, usually the secondary, 
is on the rotating member. The secondary winding receives power 
from the primary by electromagnetic induction. 


ROTATING MACHINES 


37 


4026 Induction Generator. —An induction generator is a machine 
structurally identical with an induction motor, but driven above 
synchronous speed as an alternating-current generator. 

4027 Engine Type Generator. —An engine type generator is one 
coupled to an engine in such a way that it cannot be run in¬ 
dependently of the engine. 

4028 Unipolar or Acyclic Machine. —A unipolar, or acyclic machine, is 
a direct-current machine, in which the voltage generated in the 
active conductors maintains the same direction with respect to 
those conductors. 

Speed Classification of Motors. 

4036 Constant-Speed Motor. —A constant speed motor is one whose 
speed is either constant or does not materially vary; such as a 
synchronous motor, an induction motor with small slip, and an 
ordinary direct-current shunt motor. 

4036 Multispeed Motor (or Change Speed Motor). —A multispeed 
motor is a motor which can be operated at any one of several dis¬ 
tinct speeds (these speeds being practically independent of the 
load), but which cannot be operated at intermediate speeds. 

4037 Adjustable-Speed Motor. —An adjustable-speed motor is one 
in which the speed can be varied gradually over a considerable 
range, but when once adjusted remains practically unaffected by 
the load; such as a shunt motor designed for a considerable range 
of speed variation. 

4038 Base Speed of an Adjustable-Speed Motor.— The base-speed 
of an adjustable-speed motor is that speed of the motor obtained 
with full field under full load with no resistor in the armature circuit. 

4039 Varying-Speed Motor. —A varying speed motor is one whose 
speed varies with the load, ordinarily decreasing when the load 
increases; such as a series motor, a compound-wound motor, and 
a series-shunt motor. As a subclass of varying-speed motors, 
may be cited adjustable varying-speed motors, or motors in which 
the speed can be varied over a considerable range at any given 
load, but when once adjusted, varies with the load; e. g., compound- 
wound motors arranged for adjustment of speed by varying the 
strength of the shunt field. 

Classification of Rotating Electric Machines Relative to their Degree of 

Enclosure. 

4041 Open Machine. —An open machine is of either the pedestal¬ 
bearing or end bracket type where there is no restriction to venti¬ 
lation, other than that necessitated by good mechanical construction. 

4042 Protected Machine. —A protected machine is one in which the 
armature, field coils, and other live parts are protected mechanic¬ 
ally from accidental or careless contact, while free ventilation is 
not materially obstructed. 


38 


STANDARDS OF THE A. I. E. E. 


4043 Enclosed Ventilated Machine.—An enclosed ventilated (or semi- 
enclosed) machine is one in which the ventilating openings in the 
frame are protected with wire screen, expanded metal, or other 
suitable perforated covers, having apertures not exceeding 3^ square 
inch (3.2 sq. cm.) in area. See §4316. 

4044 Totally Enclosed Machine.—A totally enclosed machine is one 
so enclosed as to prevent circulation of air between the inside and 
the outside of the case, but not sufficiently to be termed air-tight. 

4046 Separately Ventilated Machine.—A separately ventilated machine 
has its ventilating air supplied by an independent fan or blower 
external to the machine. 

4046 Self-Ventilated Machine.—A self-ventilated machine differs 
from a separately ventilated machine only in having its ventilating 
air circulated by a fan, blower, or centrifugal device integral with 
the machine. 

If the heated air expelled from the machine is conveyed away 
through a pipe attached to the machine, this should be so stated. 

4047 Water-Cooled Machine.—A water-cooled machine is one which 
mainly depends on water circulation for the removal of its heat. 

4048 Drip-Proof Machine.—A drip-proof machine is one so protected 
as to exclude falling moisture or dirt. A drip proof machine may 
be either open or semi-enclosed, if it is provided with suitable pro¬ 
tection integral with the machine, or so enclosed as to exclude 
effectively falling solid or liquid material. 

4061 Explosion-Proof Machine (or Flame-Proof Machine).—An ex¬ 
plosion-proof machine is a machine in which the enclosing case can 
withstand, without injury, any explosion of gas that may occur 
within it, and will not transmit the flame to any inflammable gas 
outside it. 

4062 Machine with Explosion-Proof Slip-Ring Enclosure.—A machine 
in which the slip rings and' brushes alone are included within an 
explosion-proof case should not be described as an explosion-proof 
machine, but as a machine with explosion-proof slip-ring en¬ 
closure. 

Classification of Alternating-Current Commutator Motors. 

(An alternating current commutator motor may be classified under more 
than one of the following groups.) 

Classification by Phases of Energy Supply. 

4061 Single-Phase Commutator Motor.—A single-phase commutator 
motor is one that receives the whole of its energy from only one 
phase of an alternating-current supply system, without requiring 
external phase-converting apparatus. 

4062 Polyphase Commutator Motor.—A polyphase commutator motor 
is one that receives its energy from a plurality of phases of an alter¬ 
nating-current supply system, or from a single-phase system through 
phase-converting apparatus external to the motor. 


ROTATING MACHINES 


39 


Classification by Speed Characteristics. 

4063 General.—For convenience, alternating-current commutator motors 
may be classified with reference to their speed characteristics as 
(1) constant-speed motors, (2) multi-speed motors, (3) adjustable- 
speed motors, and (4) varying-speed motors. Definitions of these 
terms as given in §§ 4036 to 4039 for motors in general, should 
be adopted for alternating-current commutator motors, in so far 
as they are applicable. 

Classification by Excitation. 

4064 Stator-Excited Commutator Motor.—A stator-excited commu¬ 
tator motor is one in which the torque-producing field is due to a 
current in a winding located on the stator. By the “torque pro¬ 
ducing field” is meant that component of the magnetic field which, 
with the in-phase component of the • current, produces the torque 
of the motor. 

4066 Rotor-Excited Commutator Motor.—A rotor-excited commutator 
motor is one in which the torque-producing field is due to a current 
in a winding located on the rotor. See §4064. 

4066 Stator- and Rotor-Excited Commutator Motor.—A stator- and 
rotor-excited commutator motor is one in which the torque pro¬ 
ducing field is due to currents in windings located on the stator and 
on the rotor. See §4064. 

4067* Constant-Field Commutator Motor.—A constant-field commu¬ 
tator motor is one in which the torque-producing field remains 
practically constant, independent of the load. See §4064. 

4068* Varying-Field Commutator Motor.—A varying-field commutator 
motor is one in which the torque-producing field varies in some pro¬ 
portion with the current in the armature (which latter is generally 
the rotor.) See §4064. 

Classification by Neutralization and Compensation. 

4069 Neutralized Commutator Motor.—A neutralized commutator 

motor is one in which use is made of a winding for producing a 
magnetizing force which at each instant and at each point in the 
air-gap under the pole face is practically equal and opposite to the 
magnetizing force due to the armature current. 

4070 Compensated Commutator Motor.—A compensated commutator 
motor is one in which means, other than a neutralizing winding, 
are provided within the motor for improving the power-factor. 

Classification by Energy Reception 

4071 Conduction Commutator Motor.—A conduction commutator 

motor is one in which the working energy is supplied to only one 

(4067) Alternating-current commutator motors of this class will in general have 
load-speed characteristics similar to those of the direct-current shunt motor, but not all 
alternating-current commutator motors having such load-speed characteristics are con¬ 
stant-field machines. 

(4068) Such a motor will in general have load-speed characteristics similar to those 
of the direct-current series motor. 



40 


STANDARDS OF THE A. I. E E. 


of the members, and is conveyed to it by conduction. By “work¬ 
ing energy” is meant the energy which is directly converted into 
mechanical energy, and which includes the shaft energy output 
plus core losses and friction. 

4072 Transformer Commutator Motor.—A transformer commutator 
motor is one in which the working energy is transmitted from one 
member to the other by transformer action. 

A motor in which the energy required by its armature (which is 
generally the rotor) is conveyed to it by electromagnetic induction 
or transformer action, may properly be referred to either as an 
“induction motor,” or as a “transformer motor”. Although it is 
equally applicable to a motor having a commutator, the term “in¬ 
duction motor” is usually applied to a motor without a commutator. 
The term “transformer commutator motor” is therefore recom¬ 
mended for use with motors of the induction, or transformer type, 
having commutators. 

4073 Transformer-Conduction Commutator Motor.—A transformer- 

conduction commutator motor is one in which the energy required 
by its armature (which is generally the rotor) is conveyed to it by 
both conduction and electromagnetic induction. 

4074 Repulsion Commutator Motor.—A repulsion commutator motor 
is a transformer commutator motor in which use is made of brushes 
for short-circuiting a number of coils of the commutated winding. 


Miscellaneous Definitions 


4086 Saturation Factor.—The saturation factor of a machine is the 
ratio of a small percentage increase in field excitation to the cor¬ 
responding percentage increase in voltage thereby produced. Un¬ 
less otherwise specified, the saturation factor of a machine refers 
to the no-load excitation required at normal rated speed and voltage. 
It is determined from measurements of saturation made on open 
circuit at rated speed. 

4086 Percentage Saturation.—The percentage saturation of a machine 
at any excitation may be found from its saturation curve (generated 
voltage as ordinates, agaihst excitation as abscissas), by drawing 
a tangent to the curve at the ordinate corresponding to the as¬ 
signed excitation, and extending the tangent to intercept the axis 
of ordinates drawn through the origin. The ratio of the intercept 
on this axis to the ordinate at the assigned excitation, when ex¬ 
pressed in per cent, is the percentage saturation, and is independent 
of the scales selected for excitation and voltage. This ratio as a 
fraction, is equal to the reciprocal of the saturation-factor at the 
same excitation, deducted from unity; or, if / be the saturation 
factor and p the percentage saturation, 



ROTATING MACHINES 


41 


4088* Variation in Alternators.—The variation in alternators, or 
alternating-current circuits in general is the maximum angular 
displacement, expressed in electrical degrees (see §3222) of cor¬ 
responding ordinates of the voltage wave and of a wave of 
absolutely constant frequency equal to the average frequency of 
the alternator or circuit in question, and may be due to the varia¬ 
tion of the prime mover. See §§ 14010 and 14011. 

4089 Per cent Resistance Drop.—The per cent resistance drop in an 
electric machine is the ratio of the internal resistance drop at 75° C. 
to the terminal voltage expressed in per cent. 

Unless otherwise specified this per cent drop shall be referred to 
rated load and rated power factor. 

The per cent resistance drop in an induction motor is expressed 
in terms of the internally induced electromotive force. 

4090 Per cent Reactance Drop.—The per cent reactance drop in an 
electric machine or apparatus is the ratio of the internal reactance 
drop to the terminal voltage, expressed in per cent. 

Unless otherwise specified this per cent drop shall be referred to 
rated load and rated power factor. 

The per cent reactance drop in an induction motor is expressed 
in terms of the internally induced electromotive force. 

4091 Per cent Impedance Drop.—The per cent impedance drop in an 
electric machine is the ratio of the internal impedance drop at 75° C. 
to the terminal voltage, expressed in per cent. 

Unless otherwise specified this per cent drop shall be referred to 
rated load and rated power factor. 

The per cent impedance drop in an induction motor is expressed 
in terms of the internally induced electromotive force. 

4092 Magnetic Degree.—A magnetic degree is the 360th part of the 
angle subtended, at the axis of a machine, by a pair of its field poles. 
One mechanical degree is thus equal to as many magnetic degrees as 
there are pairs of poles in the machine. 

4094 Regulation of D-C. Generators.—The regulation of a d-c. genera¬ 
tor is usually stated by giving the numerical values of the voltage 
at no load and rated load, and in some cases it is advisable to state 
regulation at intermediate loads. The regulation of d-c. generators 
refers to changes in voltage corresponding to gradual changes in 
load, and does not relate to the comparatively large momentary 
fluctuations in voltage that frequently accompany instantaneous 
changes in load. 

4095 Regulation of Constant-Potential A-C. Generators.—In con¬ 
stant-potential a-c. generators, the regulation is the rise in voltage 
(when the specified load at specified power factor is reduced to zero) 
expressed in per cent of normal rated-load voltage. 

4096 Regulation of Constant-Current Machines.—In constant-current 
machines the regulation is the ratio of the maximum difference of 

(4088) If p is the number of pairs of poles, the variation of an alternator is p times 

the variation of its prime mover, if direct-connected, and pn times the variation of the prime 

mover if rigidly connected thereto in such a manner that the angular speed of the alternator 

is « times that of the prime mover. 



42 


STANDARDS OF THE A. I. E. E. 


current from the rated-load value (occurring in the range from 
rated-load to short-circuit, or minimum limit of operation), to the 
rated-load current. 

4097 Regulation of Constant-Speed Motors.—In constant-speed direct- 
current motors and induction motors, the regulation is the ratio of 
the difference between full-load and no-load speeds to the no-load 
speed. 

4098 Regulation of Converters, Dynamotors, Motor-Generators and 
Frequency Converters.—In converters, dynamotors, motor-genera¬ 
tors, and frequency converters, the regulation is the change in the 
terminal voltage of the output side between the two specified loads. 
This may be expressed by giving the numerical values, or as the 
percentage of the terminal voltage at rated load. 

OPERATION 
Temperature Limits 

4105 Exceptions to General Temperature Limits Given in Chapter II.— 

(a) Railway Motors: See §§5202 and 6101. 

(b) Automobile Propulsion Machines: See §6206. 

(c) Railway Substation Machines: See §§5201 and 5102. 

(d) Squirrel Cage and Amortisseur Windings. The temperature 
may attain any value such as will not occasion mechanical injury to 
the machine. 

(e) Field Control Railway Motors: See §5204. 

4106 Collector Rings.—The observable temperature of collector rings 
shall not be permitted to exceed the values set forth in §2231 (c) 
for the insulations employed either in the collector rings themselves 
or in adjacent insulations whose life would be affected by the heat 
from the collector rings. 

4107 Commutators.—The observable temperature shall in no case be 
permitted to exceed the values given in §2231 (c) for the insulation 
employed either in the commutator or in an insulation whose life 
would be affected by the heiat of the commutator. These tempera¬ 
ture limits are intended only to protect the insulation of the com¬ 
mutator and of the adjacent parts and are not intended as a criterion 
of successful commutation. 

4108 Cores.—The observable temperature of those parts of the iron 
core in contact with insulating materials shall in no case be permitted 
to exceed the values given in §§2231 (c) for the insulation employed. 

4109 Other Parts, (Such as Brush-Holders, Brushes, Bearings, Pole- 
Tips, Cores, etc.)—All parts of electrical machinery other than those 
whose temperature affects the temperature of the insulating material 
may be operated at such temperatures as shall not be injurious in 
any other respect. 

4110 Maximum Temperature Rise in Service.—Whatever may be the 
ambient temperature when the machine is in service, the limits of 
the maximum observable temperature or of temperature rise specified 
in the rules should not be exceeded in service; for, if the maximum 


ROTATING MACHINES 


43 


temperature be exceeded, the insulation may be endangered, and if 
the rise be exceeded, the excess load may lead to injury, by exceeding 
limits other than those of temperature; such as commutation, stalling 
load and mechanical strength. For similar reasons, loads in excess 
of the rating should not be taken from a machine. 

RATING 

Units in Which Rating Shall be Expressed 

4220 Rating of D-C. Generators.—The rating of direct-current gen¬ 
erators, shall be expressed in kilowatts (kw.) available at the termi¬ 
nals at a specified voltage. 

4221 Rating of Alternators.—The rating of alternators shall be expressed 
in kilovolt-amperes (kv-a.) available at the output terminals, at a 
specified voltage and power factor. 

4222* Rating of Motors.—It is strongly recommended that the rating 
of motors shall be expressed in kilowatts (kw.) available at the shaft. 
(An exception to this rule is made in the case of railway motors, 
which, for some purposes, are also rated by their input. See §5203. 
4223 Rating of Auxiliary Machinery.—Auxiliary machinery, such as 
regulators, balancer sets, synchronous-condensers, etc., shall have 
their ratings appropriately expressed. It is also essential to specify 
the voltage (and frequency, if a-c.), of the circuits on which the 
machinery may appropriately be used. 

Limitations other than Temperature Rise 
4260* Mechanical Limitations.— *(a ) General : All types of rotating 
machines shall be so constructed that they will safely withstand 
an over-speed of 25 per cent, except in the case of steam turbines, 
which, when equipped with emergency governors, shall be constructed 
to withstand 20 per cent over-speed. 

( b ) Generators: Water-wheel generators shall be constructed for 
the maximum runaway speed which can be attained by the combined 
unit. 

(c) Motors: Motors for continuous service shall, except when 
otherwise specified, be required to develop running torque at least 
175 per cent of that corresponding to the running torque at their 
rated load, without stalling. Obviously, duty-cycle machines must 
carry their peak loads without stalling. 

(4222) Since the input of machinery of this class is measured in electrical units and 
since the output has a definite relation to the input, it is logical and desirable to measure 
the delivered power in the same units a3 are employed for the received power. There¬ 
fore, the output of motors should be expressed in kilowatts instead of in horse power. 
However, on account of the hitherto prevailing practise of expressing mechanical output 
in horse power, it is recommended that for machinery of this class the rating should, for 
the present, be expressed both in kilowatts and in horse power; as follows: 

Kw.-Approx, equiv. h.p.- 

For the purposes of these rules the horsepower shall be taken as 746.0 watts. 

In order to lay stress upon the preferred future basis, it is desirable that on rating 
plates, the rating in kilowatts shall be shown in larger and more prominent characters 
than the rating in horse power. 

One kilowatt is equal to 102 kilogrammeters per second. 

(4250-a) In the case of series motors, it is impracticable to specify percentage values 
for the guaranteed overspeed, on account of the varying service conditions. 





44 


STANDARDS OF THE A. I. E. E. 


4251 Commutation Limitations.— (a) Continuously Rated Machines: 
Continuously rated machines shall be required to commutate suc¬ 
cessfully momentary loads of 150 per cent of the amperes correspond¬ 
ing to the continuous rating, keeping the rheostat set for rated load 
excitation. Successful commutation is such that neither brushes 
nor commutator are injured by the test. See §§2220 and 5203. 

(b) Machines for Duty-Cycle Operation : Machines for duty-cycle 
operation with widely fluctuating loads, shall commutate success¬ 
fully under their specified operating conditions. See §§2222 and 
2223. 

4262 Limitations of Stability.—Continuously rated machines shall be 
required to carry momentary loads of 150 per cent of the amperes 
corresponding to the continuous rating, keeping the rheostat set for 
rated load excitation. 

In the Case of direct-connected generators, this clause is not to 
be interpreted as requiring the prime mover to drive the generator 
at this overload. 

TESTS 

Ambient Temperature 

4300 Measurement of the Ambient Temperature During Tests of 
Machines.—(See §2300) (a) Machines Cooled by Forced Draught : In 
the testing of rotating machines, cooled by forced draught, a conven¬ 
tional weighted mean shall be employed, a weight of four being given 
to the temperature of the circulating air supplied through ducts and 
a weight of one to the surrounding room air. See §2300 Note. 

( b) Machines Below Floor Line : Where machines are partly 
below the floor line in pits, the temperature of the rotor shall be 
referred to a weighted mean of the pit and room temperatures, the 
weight of each being based on the relative proportions of the rotor 
in and above the pit. Parts of the stator constantly in the pit shall 
be referred to the ambient temperature in the pit. 

Machine Temperatures 

4316 Machines with Small Ventilating Apertures.—Machines having 
ventilating openings smaller than 0.02 sq. in. (0.13 sq. cm.) in 
area, when intended to be operated in locations or under conditions 
where the openings are liable to become clogged, should be con¬ 
sidered as totally enclosed machines and tested as such with 
openings closed, and in all cases the rating on this basis should be 
indicated on the rating plate. 

4319 Exception to Temperature Limits Used in Method 1.—In the 

case of enclosed motors and generators, the limits of the observable 
temperature rise shall be 5°C. higher than allowed by the general 
rule. This rule does not apply to those types of machines defined 

in §§ 4043, 4045 and 4046. 

4320 Exception to Temperature Limits Used in Method 2.—In the 

case of enclosed motors and generators, the limits of the observable 
temperature rise shall be 5°C. higher than allowed by the general 
rule. This rule does not apply to those types of machines defined 

in §§. 4043, 4045 and 4046. 


ROTATING MACHINES 


45 


4321 Method of Temperature Measurement Used in Determining 
Temperature of Stators of Machines.—Method 3 should be 
applied to all stators of machines with cores having a width of 50 cm. 
(20 in.) or over. It should also be applied to all machines of 5000 
volts or more, if rated over 500 kv-a., regardless of core width. 

Efficiency 

4334* Classification of Losses.—Losses are classified as shown in Table 
401. 

4335 Losses to be Considered in Machines.—Conventional efficiencies 
shall be based upon the losses listed in Table 402, and these losses 
shall be measured as specified in §§4336-4342 inclusive. 

TABLE 401 


Classification of Losses in Machinery 


Accurately Measurable 

Approximately 
Measurable or 
Determinable 

Indeterminable 

No-load core losses, 
including eddy- 

current losses in 
conductors at no- 
load 

Brush Friction loss 

Iron loss due to flux 
distortion 

Load 1 2 R losses in 
windings 

No-load I 2 R losses 
in windings 

i 

Brush-contact loss 

Eddy-current losses 
in conductors due 
to transverse fluxes 
occasioned by the 
load currents 


Losses due to 
windage and to 
bearing friction 

Eddy-current 1 o s- 
ses in conductors 
due to tooth sat¬ 
uration resulting 
from distortion of 
the main flux 



Tooth-frequency los¬ 
ses due to flux 
distortion under 
load 


Dielectric losses 

Short-circuit loss of 
commutation 


(4334) The losses in constant-potential machinery, either of the stationary type, or of 
the constant-speed rotary type, are of two classes; namely, those which remain substantially 
constant at all loads, and those which vary with the load. . The former include iron losses, 
windage and friction, also 7 2 R losses in any shunt windings. The latter include /* R 

















46 


STANDARDS OF THE A. I. E. E. 


4336 P R Loss—(a) General: The PR loss shall be based upon the 
current and the measured resistance. 

(i) Polyphase Induction-Motor Rotor: The PR loss in the rotors 
of polyphase induction motors should be determined from the slip, 
whenever the latter is accurately determinable, using the following 
equation: 


Rotor / 2 R loss = 


output X slip 
1 — slip 


* TABLE 402 


Losses in Rotating Electric Machines 

(References are to Sections) 



I 2 R 

Loss 

Windings 

Friction 

and 

Windage 

Brush 

Friction 

Core 

Loss 

Brush 
Contact 
l 2 R Loss 

Stray 

Load 

Losses 

D-C commutat- 





4341 


ing machines 

4336(a) 

4337(a) 

4338 

4339 

5341 

Note 5 

(Note 1) 







A-C commutat- 






Note 5 

ing machines 

4336(a) 

4337(a) 

4338 

4339 

4341 

5339 

(Note 1) 







Railway motors 

4336(a) 

5337 

5338 

5339 

4341 

Note 5 



5338 

5339 



5339 

Synchronous 







motors and gen- 

4336(a) 

4337(a) 

4338 

5339 

4341 

4342(b) 

erators (Note 4) 



Note 3 

4339 

Note 3 


Synchronous 

4336(c) 

4337(a) 

4338 

4339(a) 


Note 5 

converters 




4339(b) 



Induction 

4336(b) 

4337(a) 

4338 

4339(a) 

4341 

4342(b) 

machines 




4339(c) 

Note 2 



Notes:—(1) Except railway motors. 

(2) When there are collector rings. 

(3) Brush friction and brush contact losses are negligible except in the case of 
revolving armature machines. 

(4) For the booster type of synchronous converter, where the booster forms an 
integral part of the unit, its losses shall be included in the total converter losses in 
estimating the efficiency. 

(5) These losses, while usually of low magnitude, are erratic, and the Institute 
is not at this time prepared to make recommendations for approximating them. 

losses in series windings. The constant losses may be determined by measuring the power 
required to operate the machine at no load, deducting any series I 2 R losses. The variable* 
loss at any load may be computed from the measured resistance of the series windings and 
the given load current. 

(4335) This simple method of determining the losses and hence the efficiency is only 
approximate, since the losses which are assumed to be constant do actually vary to some 
extent with the load, and also becaue the actual loss in the copper windings is sometimes 
appreciably greater than the calculated 1 2 R loss. The difference between the approximate 
losses, as above determined, and the actual losses, is termed “stray load losses.” These 
latter are due to distortions in electric or magnetic fluxes from their no-load distributions or 
values, brought about by the load current. They are usually only approximately measur¬ 
able, or may be indeterminable, but certain of them reach values in various kinds of ma¬ 
chinery, which require that they should be taken into account. 

Dielectric losses are usually negligible. 

The stray load losses include the items in the column of Table 401 headed “Indeter¬ 
minable” but do not include the increased core losses due to increased excitation for 
compensating internal drop under load. 
















ROTATING MACHINES 


47 


In large slip-ring motors, in which the slip cannot be directly 
measured by loading, the rotor 1 2 R loss shall be determined by 
direct resistance measurement; the rotor full-load current to be 
calculated by the following equation: 

„ . watts output 

Current per ring = - -= - 

rotor voltage at stand-still X v 3 XK 

This equation applies to three-phase rotors. For rotors wound 
for two phase, use 2 instead of the \/3. K may be taken as 0.95 
for motors of 150 kw. or larger. The factor K usually decreases as 
the size of motor is reduced, but no specific value can be stated for 
smaller sizes. 

(c) Synchronous Converter : The I 2 R losses in the armature 
winding shall be derived from those corresponding to its use as a 
direct-current generator, by using suitable factors. 

4337 Bearing Friction and Windage.— (a) General: Drive the machine 
from an independent motor, the output of which shall be suitably 
determined. The machine under test shall have its brushes removed 
and shalLnot be excited. This output represents the bearing friction 
and windage of the machine under test. 

(6) Induction Motors : The bearing friction and windage of in¬ 
duction motors may be measured by running motors free at the 
lowest voltage at which they will rotate continuously at approxi¬ 
mately rated speed; the watts input, minus PR loss, under these 
conditions being taken as the friction and windage. 

(c) Engine-Type Generators: In the case of engine-type gener¬ 
ators, (See §4027) the windage and bearing friction loss is ordinarily 
very small, amounting to a fraction of one per cent of the output. This 
loss shall be neglected owing to its small value and the difficulty 
of measuring it. 

(< d ) D. C. Railway Motors: See §5337. 

4338 Brush Friction of Commutator and Collector Rings.— (a) General: 
Drive the machine from an independent motor, the output of which 
shall be suitably determined. The brushes shall be in contact with 
the commutator or collector rings, but the machine shall not be 
excited. The difference between the output obtained in the test 
in §4337 and this output shall be taken as the brush friction. The 
surfaces of the commutator and brushes should be smooth and glazed 
from running when this test is made. 

(b) D. C. Railway Motors: See §5338. 

4339 Core Losses.—( a) General: Drive the machine from an inde¬ 
pendent motor, the output of which shall be suitably determined. 
The brushes shall be in contact, and the machine shall be excited, 
so as to produce at the terminals a voltage corresponding to the 
calculated internal voltage for the load under consideration. The 
difference between the output obtained by this test and that ob¬ 
tained by test under §4338 (a) shall be taken as the core loss. 

( b ) Synchronous Machines: The internal voltage of synchronous 
machines shall be determined by correcting the terminal voltage 
for the resistance drop only. 



48 


STANDARDS OF THE A. I. E. E. 


(c) Induction Motors: The core loss of an induction motor may 
be determined by measuring the watts input to the motor when 
running free at rated voltage and frequency and subtracting there¬ 
from the no-load copper loss, bearing friction and windage. 

(d) D. C. Railway Motors : See §5339. 

4341* Brush-Contact P R Loss. — (a) General : One volt drop per 
brush shall be considered as the Institute standard drop corres¬ 
ponding to the PR brush-contact loss, for carbon and graphite 
brushes with pigtails attached. One and one-half volts per brush 
shall be allowed where pigtails are not attached. Metal-graphite 
brushes shall be considered as special. 

(b) Automobile Motors : See §5341. 

4342* Stray Load-Losses.—(a) Synchronous Machines : These include 
iron losses, and eddy-current losses in the copper, due to fluxes 
varying with load and also to saturation. 

Stray load-losses shall be determined by operating the machine 
on short circuit and at rated-load current. This, after deducting 
the windage and friction and PR loss, gives the stray, load-loss for 
polyphase generators and motors. These losses in* single-phase 
machines are large; but the Institute is not yet prepared to specify 
a method for measuring them. 

( b) Induction Machines: These include eddy-current losses in the 
stator copper, and other eddy-current losses due to fluxes varying 
with the load. In windings consisting of relatively small conductors, 
these eddy-current losses are usually negligible. 

With rotor removed, measure the power input to the stator with 
different values of current at the rated frequency. The curve 
plotted with these values gives the combined PR and stray load- 
losses due to eddy-currents in the stator copper. Deduct the PR 
loss determined from the resistance, and the difference will represent 
the stray load-losses corresponding to the various currents. While 
this method is not accurate for some types of motors it usually 
represents a sufficiently good approximation. 

(4341) The brush-contact / 2 R }pss depends largely upon the material of which the brush 
is composed. 

As indicating the range of variation the following table will be of interest: 


TABLE 403 
Brush-Contact Drop 


Grade of brush 

Volts drop across one brush-contact 
(Average of positive and negative brushes) 

Hard carbon.. 

Soft carbon. 

Graphite. 

Metal-graphite types. 

1.1 

0.9 

0.5 to 0.8 

0.15 to 0.5 (The former for largest proportion 
of metal) 


• (4342) Values of the indeterminate losses may also be obtained by brake or other direct 
test and used in estimating actual efficiencies of similarmachinesby the separate-loss method. 










ROTATING MACHINES 


49 


4343 Miscellaneous Losses.—(a) Field-Rheostat Losses: Field-Rheostat 
losses shall be included in the generator losses where there is a field 
rheostat in series with the field magnets of the generator, even 
when the machine is separately excited. 

(b) Ventilating Blower: When a blower is supplied as part of a 
machine set, the power required to drive it shall be charged against 
the complete unit, but not against the machine alone. 

(■ c ) Other Auxiliary Apparatus: Auxiliary apparatus, such as a 
separate exciter for a generator or motor, shall have its losses charged 
against the plant of which the generator and exciter are a part, and 
not against the generator. An exception should be noted in the 
case of turbo-generator sets with direct-connected exciters, in which 
case the losses in the exciter shall be charged against the generator. 
The actual energy of excitation and the field-rheostat losses, if any 
shall be charged against the generator. See §4343 (a). 

Wave Shape 

4351 Deviation Factor of a Wave.—The deviation factor of the open cir¬ 
cuit terminal voltage wave of synchronous machines shall not ex¬ 
ceed ten per cent unless otherwise specified. See §3274. 

4352* Telephone Interference Factor of a Wave. (For trial only.) 
(See §3278.)—(a) Conditions of Test. The weighting of the sine 
wave components of different frequencies shall be as given in Fig. 
4—1. 



FREQUENCY-CYCLES PEJR SECOND 
Fig. 4-1 

The telephone interference factor of a voltage wave, corresponding 
to this weighting, may be measured by the use of the network shown 
in Fig. 4—2. 






































50 


STANDARDS OF THE A. I. E. E. 



o R 4 —oMeter 


R 


o 

o' 


5 



Ci =0.9 mf, 
C 2 = 0.9 « 


Network Constants 
Li =0.023 henry ] 


#i =5 ohms ±2% 
#2 = 12 “ ± 2 % 
#3 =73 “ ±1% 

# 4 = 22.5 “ ± 2 % 
# 5=43 “ ± 1 % 


C 4 = 7.5 “ 



# 4 = 0.019 


J 


Fig. 4-2 


With this network the telephone interference factor of a voltage 
wave is the ratio of the current I in micro-amperes in the meter branch 
of the network to the voltage E applied to the external terminals 
of the network. The measurement may be made on the low 
tension side of a potential transformer. A sensitive vacuum thermo¬ 
couple provided with a shunt, and a direct-current mil-ammeter 
have been found convenient for measuring the current. 

(b) The appropriate limiting value of the telephone interference 
factor of a wave (.See §3278), either for machines or for circuits, 
has not yet been determined, and. cannot now be specified. The 
whole matter of interference, including reasonable requirements for 
both power and communication systems, is under discussion, in 
consultation with power, telephone, and other interests concerned. 

Tests of Dielectric Strength 

4358 Frequency of Test Voltage.—In d-c. machines, and in general 
commercial application of a-c. machines, the testing frequency of 
60 cycles per second is recommended. 

4361* Exceptions to Standard Test Voltage Given in Section 2366. 

(a) Field Windings of Alternating Current Generators : Field 
windings of alternating current generators shall be tested with 
10 times the exciter voltage, but in no case with less than 1500 volts 
nor more than 3500 volts. 

*(b) Field Windings of Synchronous Machines : Field windings 
of synchronous machines including motors and converters which 
are to be started with alternating current are to be tested as follows: 

When machines are to be started with field short circuited, the 
field windings shall be tested as specified in §4361 (a). 

When machines are to be started with fields open circuited and 

(4361-6) Series field windings should be regarded as part of the armature circuit and 
tested as such. 




















ROTATING MACHINES 


51 


sectionalized while starting, the field windings shall be tested with 
5000 volts. 

When machines are to be started with fields open circuited and 
connected all in series while starting, the windings shall be tested 
with 5000 volts for less than 275 volts excitation and 8000 volts for 
excitation of 275 volts to 275 volts. 

*<c) Phase-Wound Rotors of Induction Motor : The secondary 
windings of wound rotors of induction motors shall be tested with 
twice their normal induced voltage, plus 1000 volts. When induction 
motors with phase-wound rotors are to be reversed, while running 
at approximately normal speed, by reversing the primary connections, 
the test shall be four times the normal induced voltage plus 1000 
volts. 

(d) Small Motors and Generators : Small machines taking not over 
660 watts or having an output not exceeding h. p. (373 watts), 
such as fractional hofse power motors, and intended solely for opera¬ 
tion on supply circuits not exceeding 275 volts, shall be tested with 
900 volts. 

(e) Alternating Current Machines Connected to Permanently 
Grounded Single-Phase Systems: Alternating current machines con¬ 
nected to permanently grounded single-phase systems, for use on 
permanently grounded circuits operating at more than 300 volts 
shall be tested with 2.73 times the voltage of the circuit to ground, 
plus 1000 volts. This does not refer to three-phase machines with 
grounded star neutral. 

*(f) Machines for Use on Circuits of 25 Volts or Lower: Machines 
for use on circuits of 25 volts or lower, such as bell ringing apparatus, 
electric machines used in automobiles, machines used on low voltage 
battery circuits, etc., shall be tested with 500 volts. 

Regulation 

4390 Conditions for Tests of Regulation (See §2390).— (a) Power 
Factor: In alternating current generators the power factor of the 
load to which the regulation refers should be specified. Unless 
otherwise specified, it shall be understood as referring to non- 
inductive load, that is, to a load in which the current is in phase 
with the e. m. f. at the terminals of the machine. 

( b ) Excitation: In communtatirlg machines, rectifying machines 
and synchronous machines, the regulation shall be determined under 
such conditions as to maintain the field adjustment constant at 
a value which gives rated-load voltage at rated-load current. These 
conditions are as follows: 

In the-case of separately excited fields: constant excitation. 

In the case of shunt machines: constant resistance In the sliunt- 
field circuit. 

In the case of series or compound machines:, constant resistance 
shunting the. series field windings. 

4394* Tests and Computation of Regulation of A-C. Generators. — (a) 

Methods Available: The regulation of alternating-current gen- 
(4361-c) By normal induced voltage is here meant the voltage between slip rings on open 
circuit at standstill with normal voltage impressed on the primary. 

(4361-/) The present National Electrical Code limit for a single outlet is 660 watts. 



52 


STANDARDS OF THE A. I. E. E. 


erators may be determined by any one of the three following 
methods, which are given in the order of preference: 

(b) Method I. By Loading: The regulation can be measured 
directly, by loading the generator at the specified output and power 
factor, then reducing the load to zero, and measuring the terminal 
voltage, with speed and excitation adjusted to the same values 
as before the change. This method is not generally applicable for 
shop tests, particularly on large generators and it becomes necessary 
to determine the regulation from such other tests as can be readily 
made. 

*(c) Method II. From Test Curves: This method consists in 
computing the regulation from experimental data of the open- 
circuit saturation curves and the zero-power-factor saturation 
curve. The latter curve, or one approximating very closely to 
it, c an be obtained by over-exciting the generator while carrying 

(4394-c) Method II for deducing the load saturation curve, at any assigned power 
factor, from no-load and zero power-factor saturation curves obtained by test, must be 
regarded as empirical. Its value depends upon the fact that experience has demonstrated 
the reasonable correctness of the results obtained by it. 





Fig. 4-4 


Fig. 4-5 













ROTATING MACHINES 


53 


a load of idle-running under-excited synchronous motors. The 
power factor under these conditions is very low and the load sat¬ 
uration curve approximates very closely the zero power-factor 
saturation curve. From this curve and the open circuit curve, 
points for the load saturation curve for any specified power factor 
can be obtained by means of vector diagrams. 

*(d) Method III. From Estimated Zero Power Factor Curve 
Where it is not possible to obtain by test a zero power factor curve 
as in Method II this curve can be estimated closely from open- 

To apply method II, it is necessary to obtain from test the open circuit saturation curve 
Fig. 4-3, and the load saturation curve BCat zero power factor and rated-load current. At 
any given excitation 0 c, the voltage that would be induced on open circuit is c a, the 
terminal voltage at zero power factor is c b and the apparent internal drop is a b. The ter¬ 
minal voltage c d at any other power factor can then be found by drawing an e.m.f. diagram 
as in Fig. 4-4. where <t> is an angle such that cos <p is the power factor of the load, b e the 
resistance drop (7 R ) in the stator winding, b a the total internal drop and a c the total in* 
duced voltage; b a and a c being laid off to correspond with the values obtained from Fig.4-3. 



The terminal voltage at power factor cos <f> is then c b Fig. 4-4, which when laid off in Fig. 4 3 
gives point d. By finding a number of such points, the curve B d d' for power factor cos <f> 

100 X a'd' 

is obtained and the regulation at this power factor (expressed in per cent) is -—- 

c'd' 

since a'd' is the rise in voltage when the load at power factor cos <j> is thrown off at normal 
voltage c' d f . 

Generally, the ohmic drop can be neglected as it has little influence on the regulation, 
except in very low-speed machines where the armature drop is relatively high or in some 
cases where regulation at unity power factor is being estimated. For low power factors 
its effect is negligible in practically all cases. If resistance is neglected, the simpler diagram 
Fig. 4-5, may be used. 

(4394-d) Method III is the same as Method II except that the zero power factor curve 
must be estimated. This maybe done as follows. In Fig. 4-6, OA is the open-circuit saturation 
curve and O E the short-circuit line as obtained from test. The zero power-factor curve 
corresponding to any current B F will start from point B, and for machines designed with 
low saturation and low reactance, will follow parallel to O A as shown by the dotted curve 
B D, which is 0 A shifted horizontally parallel to itself by the distance 0 B. In high speed 
machines, or in others having low reactance, and a low degree of saturation in the magnetic 









54 


STANDARDS OF THE A. I. E. E. 


circuit and short-circuit curves, by reference to tests at zero power 
factor on other machines of similar magnetic circuit. Having 
obtained the estimated zero power-factor curve, the load saturation 
for any other power factor is obtained as in Method II, §4394 (c). 
4396 Compound Wound D-C. Generator.— In determining the regu¬ 
lation of a compound-wound d-c generator, two tests shall be made, 
one bringing the load down and the other bringing the load up, 
between no-load and rated load. These may differ somewhat, owing 
to residual magnetism. The mean of the two results shall be used. 

BIBLIOGRAPHY 
United States 

Electric Power Club: Standardization Rules. 

National Board of Fire Underwriters: National Electrical Code*. 
National Electric Light Association: Committee Reports. 

Foreign 

Associazione Elettrotecnica Italiana; Norme per 1’ ordinazione e il 
collando delle Macchine Elettriche. 

British Electrical and Allied Manufacturers’ Association: Reports. 
British Engineering Standards Association: British Standardiza¬ 
tion Rules for Electrical Machinery (exclusive of motors for trac¬ 
tion purposes); . 

Societe Internationale deis Electriciens: Bulletins. 

Union des Syndicats de 1’ Electricite: Instructions gendrales pour 
la Fourniture et la Reception des Machines electriques. 

Verband Deutscher Elektro-teehniker: Normalien, Vorschriften 
und Leitsatze. 

International 

International Electrotechnical Commission: Rating of Electrical 
Machinery and Resumes of Meetings of Delegates. 

circuit, the zero power factor curve will be quite close to B D particularly in those parts that 
are used for determining the regulation. This is the case with many turbo-generators and 
high-speed water-wheel generators. 

In many cases, however, the zerrG power-factor curve will deviate from B D, as shown by 
B C and the deviation will be npnst pronounced in machines of high reactance, high satura¬ 
tion and large magnetic leakage. .The position of curve B C with relation to B D can be 
approximated with sufficient exactness by investigating the corresponding relation as 
obtained by test at zero power factor -on machines of similar characteristics and magnetic 
circuit. Curve B C can also be calculated by methods based on the results of tests at 
zero power factor. After curve B C has- been obtained, the load saturation curve and 
regulation for any other power factor can be derived as in Method II, §4394 (c). 



ELECTRIC RA1LWA YS 


55 


CHAPTER V. 

STANDARDS FOR ELECTRIC RAILWAYS AND FOR 
AUTOMOBILE PROPULSION MACHINES 

The A. I. E. E. Standards for Electric Railways and for Automobile 
Propulsion Machines are the General Standards shown in Chapters II 
and III, and the Standards in other Chapters which are applicable to the 
devices involved together with the modifications and extensions given 
in this Chapter. 

DEFINITIONS 

General 

6000 Contact Conductors. —A contact conductor is that part of the dis¬ 
tribution system other than the traffic rails, which is in immediate 
electrical contact with the circuits of the cars or locomotives. 

Contact Rails 

6003* Contact Rail. —(a) General: A contact rail is a rigid contact 
conductor. 

*(b) Overhead Contact Rail: An overhead contact rail is a 
contact rail which is above the elevation of the maximum 
equipment line. 

(c) Third Rail: A third rail is a contact conductor placed at 
either side of the track, the contact surface of which is a few 
inches above the level of the top of the track rails. 

(d) Center Contact Rail: A center contact rail is a contact 
conductor placed between the track rails, having its contact 
surface above the ground level. 

(e) Underground Contact Rail: An underground contact rail 
is a contact conductor placed beneath the ground level. 

(f) Gage of Third Rail: The gage of a third rail is the distance, 
measured parallel to the plane of running rails, between the 
gage line of the nearer track rail and the inside gage line of the 
contact surface of the third rail. 

(g) Elevation of Third Rail: The elevation of a third rail is 
the elevation of the contact-surface of the third rail, with respect 
to the plane of the tops of running rails. 

(h) Third Rail Protection: A third rail protection is a guard 
for the purpose of preventing accidental contact with the third 
rail. 

Trolley Wires 

6004 Trolley Wire. —A trolley wire is a flexible contact conductor, 
customarily supported above the cars. 

(5003b) The maximum equipment line is the contour which embraces cross-sections of 
all rolling stock under all normal operating conditions. 



56 


STANDARDS OF THE A. I. E. E. 


6006 Messenger Wire or Cable.—A messenger wire or cable is a wire 
or cable running along with and supporting other wires, cables or 
contact conductors. 

A primary messenger is directly attached to the supporting system. 
A secondary messenger is intermediate between a primary messenger 
and the wires, cables or contact conductors. 

6006 Classes of Construction.—(a) General : Overhead trolley construc¬ 
tions are classed as Direct Suspension and Messenger or Catenary 
Suspension. 

(b) Direct Suspension: A direct suspension is the form of 
overhead trolley construction in which the trolley wires are 
attached, by insulating devices, directly to the main supporting 
system. 

(c) Messenger or Catenary Suspension: A messenger or caten¬ 
ary suspension is the form of overhead trolley construction in 
which the trolley wires are attached, by suitable devices, to one 
or more messenger cables, which in turn may be carried either 
in Simple Catenary , i.e ., by primary messengers, or in Compound 
Catenary , i.e., by secondary messengers. 

6007 Supporting Systems.—(a) General : Supporting systems for 

trolley wires shall be classed as follows: 

(b) Simple Cross-Span Systems: Simple cross-span systems 
are those having at each support a single flexible span across 
the track or tracks. 

(c) Messenger Cross-Span Systems: Messenger cross-span 
systems are those having at each support two or more flexible 
spans across the track or tracks, the upper span carrying part 
or all of the vertical load of the lower span. 

(d) Bracket Systems: Bracket systems are those having at 
each support an arm or similar rigid member, supported at 
only one side of the track or tracks. 

(e) Bridge Systems: Bridge systems are those having at each 
support a rigid member, supported at both sides of the track- 
or tracks. 

6030* Transmission System.—When the current generated for an 
electric railway is changed in kind or voltage, between the generator 
and the cars or locomotives, that portion of the conductor system 
carrying current of a kind or voltage substantially different from 
that received by the cars or locomotives, constitutes the trans¬ 
mission system. 

6031* Distribution System.—That portion of the conductor system 
of an electric railway which carries current of the kind and voltage 
received by the cars or locomotives, constitutes the distribution 
system. 

(5030 and 5031) These definitions are identical in sense, although not in words, with 
those of the Interstate Commerce Commission, as given in their Classification of Accounts 
for Electric Railways. 



ELECTRIC RAILWAYS 


57 


6032 Substation.—A substation is a group of apparatus or machinery 
which receives current from a transmission system, changes its 
kind or voltage, and delivers it to a distribution system. 

OPERATION 
Temperature Limits 

6101* Railway Motors in Continuous Service.—The following maximum 
observable temperatures are permissible in the windings of railway 
motors, when in continuous service. 

TABLE 601 

Temperatures of Railway Motors in Continuous Service. 


Class 

of Material 

Temperature 

See §1004 

By 

Thermometer 

See §1002 

By 

Resistance 

See §1002 

A 

85°C 

110°C 

B 

100°C 

130°C 


6120 Railway Substation Machines and Transformers.—Under con¬ 
ditions specified in §6201, the windings of railway substation machines 
and transformers carrying traction loads may have observable 
temperature rises 5°C in excess of the limiting observable tem¬ 
perature rises specified in Table 200. 

6130* Automobile Propulsion Machines.—On stand test, the observable 
temperature rises shall not exceed the limits specified in §6206. 

RATING 

Ratings of Railway Substation Machinery and Transformers. 

6201* Nominal Rating of Railway Substation Machines and Trans¬ 
formers.—The nominal rating of a substation machine or trans¬ 
former carrying traction loads shall be the kv-a. output at a stated 
power factor input, which, having produced a constant temperature 
in the machine or transformer may be increased 50 per cent for two 
hours, without producing temperature rises exceeding by 
more than 5°C. the limiting values given in Table 200. These 

(5101) Under extreme ambient temperatures it is permissible to operate, for short 
infrequent periods, at 15 °C. higher temperature than specified in this rule. 

(5101 and 5130) Owing to space limitations and the cost of carrying dead weight on 
vehicles, it is considered good practise to operate propulsion machinery at higher 
temperatures than would be advisable in stationary machines. (See Table 501). 









58 


STANDARDS OF THE A. I. E. E. 


machines or transformers should be capable of carrying a load of 
twice their nominal rating for a period of one minute, without dis¬ 
qualifying them for continuous service. The name plate should 
be marked “nominal rating.” 

Ratings of Railway Motors 

6202* Nominal Rating of Railway Motors. —The nominal rating of a 
railway motor shall be the mechanical output at the car or locomotive 
axle, measured in kilowatts, which causes a rise of temperature above 
the surrounding air, by thermometer, not exceeding 90°C. at the 
commutator, and 75°C. at any other normally accessible part after 
one hour’s continuous run at its rated voltage, (and frequency in the 
case of an alternating-current motor) on a stand with the motor 
covers arranged to secure maximum ventilation without external 
blower. The rise in temperature as measured by resistance, shall 
not. exceed 100°C. The statement of the nominal rating shall 
include the corresponding voltage and armature speed. 

6203* Continuous Ratings of Railway Motors. —The continuous ratings 
of a railway motor shall be the inputs in amperes at which it may be 
operated continuously at Yj Z A and full voltage respectively, without 
exceeding the observable temperature rises specified in 'fable 502, 
when operated on stand test with motor covers and cooling system, 
if any, arranged as in service. Inasmuch as the same motor may be 
operated under different conditions as regards ventilation, it will be 
necessary in each case to define the system of ventilation which is 
used. In case motors are cooled by external blowers, the flow of air 
on which the rating is based shall be given. 

TABLE 602 

Stand-Test Temperature Rises of Railway Motors 


Class 

of 

Material 

Temperature Rises 
of windings 



See §1004 

By 

Thermo¬ 

meter 

See §1002 

By 

Resis¬ 

tance 

See §1002 

A 

65°C. 

85°C. 

B 

80°C. 

105°C. 


(5201 and 5202) In the absence of any specification as to the kind of [rating the 
"nominal” rating shall be understood. 

(5203) The temperature rise in service may be very different from that on stand-test. 
See §5502 for the relation between stand-test and service temperatures as affected by 
ventilation 








ELECTRIC RAILWAYS 


59 


5204 Field-Control Railway Motors.—The nominal and continuous 
ratings of field-control motors shall relate to their performance 
with the operating field which, gives the maximum motor rating. 
Each section of the field windings shall be adequate to perform 
the service required of it, without exceeding the specified tem¬ 
perature rises. 

Ratings of Automobile Propulsion Machines 

6206 Automobile Propulsion Machines: The rating of automobile 
motors and generators shall be based upon temperature rise, on a 
stand test and with motor covers arranged as in service, fifteen 
degrees by thermometer or twenty-five degrees by resistance, above 
those of Table 200. 

Ratings of Electric Locomotives 

5210 Rating.—Locomotives shall be rated in terms of the weight on 
drivers, nominal one-hour tractive effort, continuous tractive effort 
and corresponding speeds. 

5211 Weight on Drivers.—The weight on drivers, expressed in pounds, 
shall be the sum of the weights carried by the drivers and of the 
drivers themselves. 

5212 Nominal Tractive Effort.—The nominal tractive effort, expressed in 
pounds, shall be that exerted at the rims of the drivers when the 
motors are operating at their nominal (one-hour) rating. 

6213 Continuous Tractive Effort.—The continuous tractive effort, ex¬ 
pressed in pounds, shall be that exerted at the rims of the drivers 
when the motors are operating at their full-voltage continuous rat¬ 
ing, as indicated in §5203. 

In the case of locomotives operating on intermittent service, the 
continuous tractive effort may be given for ^ or % voltage, but in 
such cases the voltage shall be clearly specified. 

6214 Speed.—The rated speed, expressed in miles per hour, shall be 
that at which the continuous tractive effort is exerted. 

TESTS 

Efficiency 

Losses in D-C. Railway Motors 

6337 Losses in Gearing and Axle Bearings.—The losses in gearing and 
axle bearings for single-reduction single-geared motors, varies with 
the type, mechanical finish, age and lubrication. The following 
values, based upon accumulated tests, shall be used in the comparison 
of single-reduction single-geared motors §5339. 


60 


STANDARDS OF THE A. I. E. E. 


TABLE 503 

Losses in Axle Bearings and Single-Reduction Gearing of Railway 

Motors 


Per cent of input 

Losses as per 

at nominal rating 

cent of input 

200 

3.5 

150 

3.0 

125 

2.7 

100 

2.5 

75 

2.5 

60 

2.7 

50 

3.2 

40 

4.4 

30 

6.7 

25 

8.5 


Note: —Further investigation may indicate the desirability of giving separate 
values of the losses for full and tapped fields, or low- and high-speed motors. 


5338. Erush Friction, Armature Bearing Friction and Windage.—The 

brush friction, armature-bearing friction and windage, shall be 
determined as a total under the following conditions: 

In making the test, the motor shall be run without gears. The 
kind of brushes and the brush pressure shall be the same as in com¬ 
mercial service. Drive the machine idle as a series motor on low 
voltage. The product of armature counter-electromotive-force and 
amperes at any speed shall be the sum of the above losses at that 
speed. See §5339. 

6339* No-Load Core Loss, Brush Friction, Armature-Bearing Friction 
and Windage.—The no-load core loss, brush friction, armature¬ 
bearing friction and windage shall be determined as a total under the 
following conditions: 

In making the test, the motor shall be run without gears. The 
kind of brushes and the brush pressure shall be the same as in com¬ 
mercial service. With the field separately excited, such a voltage 
shall be applied to the armature terminals as will give the same speed 
for any given field current as is obtained with that field current 
when operating at normal voltage under load. The sum of the losses 
above-mentioned, is equal to the product of the counter-electro- 
motive force and the armature current. 

The no-load core loss is obtained by deducting from the total 

(5339) In comparing projected railway motors, and in case it is not possible or desirable 
to make tests to determine mechanical losses, the following values of these losses, determined 
from the averages of many tests over a wide range of sizes of single-reduction single-geared 
motors, will be found useful, as approximations. They include axle-bearing, gear, armature- 
bearing, brush-friction, windage, and stray-load losses. 











ELECTRIC RAILWAYS 


61 


losses thus obtained the power required to drive the motor at cor¬ 
responding speeds as determined under §6338. 

The core loss under load shall be assumed to have the values 
given in Table 504. 

TABLE 604 

Core Loss in D-C. Railway Motors at Various Loads 


Per cent of input 
at nominal rating 

Loss as per cent 
of no-load core loss 

200 

165 

150 

145 

100 

130 

75 

125 

50 

123 

25 and under 

122 


Note: —-With motors designed for field control the core losses shall be assumed as 
the same for both full and permanent field. It shall be the mean between the no- 
load losses at full and permanent field, increased by the percentages given in the above 
Table. 


6341 Automobile Motors: When automobile motors are of low 
voltage, the great influence of brush-contact losses on the efficiency 
requires that these losses be determined experimentally for the type 
of brush used. 

CHARACTERISTIC CURVES OF RAILWAY MOTORS 

6401 General.—The Characteristic Curves of railway motors shall be 
plotted with the current as abscissas and the tractive effort, speed 
and efficiency as ordinates. In the case of a-c. motors, the power 
factor shall also be plotted as ordinates. 

6402 Voltage.—Characteristic curves of direct current motors shall be 
based upon full voltage, which shall be taken as 600 volts, or a 
multiple thereof. 

6403 Field-Control Motors.—In the case of field-control motors, charac¬ 
teristic curves shall be given for all operating field connections. 


TABLE 505. 

Approximate Losses in D-C. Railway Motors. 


Input in per cent 
of that at 
nominal rating 

Losses as per cent 
of input 

100 or over 

5.0 

75 

5.0 

60 

5.3 

50 

6.5 

40 

8.8 

30 

13.3 

25 

17.0 


The core loss of railway motors may also be determined as specified for other machines. 











62 


STANDARDS OF THE A. I. E. E. 


SELECTION OF RAILWAY MOTOR FOR SPECIFIED SERVICE 

5501 Data Required in Selecting Motor.—The following information 
relative to the service to be performed, is required, in order that an 
appropriate motor may be selected. 

(a) Weight of total number of cars in train (in tons of 2000 lb.) 
exclusive of electrical equipment and load. 

(b) Average weight of load and durations of same, and maximum 
weight of load and durations of same. 

(c) Number of motor cars or locomotives in train, and number 
of trailer cars in train. 

(d) Diameter of driving wheels. 

(e) Weight on driving wheels, exclusive of electrical equipment. 

(f) Number of motors per motor car. 

(g) Voltage at train with power on the motors—average, maxi¬ 
mum and minimum. 

(h) Rate of acceleration in miles per hour per second. 

(i) Rate of braking (in miles per hour per second). 

(j) Speed limitations, if any (including slowdowns). 

(k) Distances between stopping points. 

(l) Average duration of stops. 

(m) Schedule speed, including stops, in miles per hour. 

(n) Train resistance in pounds per ton of 2000 pounds at stated 
speeds. 

(o) Moment of inertia of revolving parts, exclusive of electrical 
equipment. 

(p) Profile and alignment of track. 

(q) Distance coasted as a percentage of the distance between stop- 
ing points. 

(r) Duration of layover at end of run, if any. 

5602* Method of Comparing Motor Capacity with Service Require¬ 
ments.—When it is not convenient to test motors under 
actual specific service conditions, recourse may be had to the follow¬ 
ing method of determining temperature rise from the stand-tests. 

The essential motor lbsses affecting temperatures in service are 
those in the motor windings, core and commutator. The mean 
service conditions may be expressed, as a close approximation, in 
terms of that continuous current and core loss which will produce 
the same losses and distribution of losses as the average in service. 

(5502) Calculation for comparing motor capacity with service requirements. The 
heating of a motor should be determined, wherever possible, by testing it in service, or with 
an equivalent duty-cycle. When the service or equivalent duty-cycle tests are not prac¬ 
ticable, the ratings of the motor may be utilized as follows to determine its temperature 
rise. 

The motor losses which affect the heating of the windings are as stated above, 
those in the windings and in the core. The former are proportional to the 
square of the current. The latter vary with the voltage and current, according to curves 
which can be supplied by the manufacturers. The procedure is therefore as follows: 

(a) Plot a time-current curve, a time-voltage curve, and a time-core loss curve for the 
duty-cycle which the motor is to perform, and calculate from these the root-mean-square 
current and the average core loss. 

(b) If the calculated r.m.s. service current exceeds the continuous rating, when run with 



ELECTRIC RAILWAYS 


63 


A stand test with the current and voltage which will give 
losses equal to those in service, will determine whether the motor has 
sufficient capacity to meet the service requirements. In service, the 
temperature rise of an enclosed motor (§4044), well exposed to the 
draught of air incident to a moving car or locomotive, will be from 75 
to 90 per cent (depending upon the character of the service) of th e 
temperature rise obtained on a stand test with the motor completely 
enclosed and with the same losses. With a ventilated motor (§4046 
and §4046), the temperature rise in service will be 90 to 100 per cent 
of the temperature rise obtained on a stand test with the same losses. 

In making a stand test to determine the temperature rise in a 
specific service, it is essential in the case of a self-ventilated motor 
(§4046) to run the armature at a speed which corresponds to the 
schedule speed in service. In order to obtain this speed it may be 
necessary, while maintaining the same total armature losses, 
to change somewhat the ratio between the I 2 R and core-loss com¬ 


ponents. 


average service core loss and speed, the motor is not sufficiently powerful for the duty- 
cycle contemplated. 

(c) If the calculated r.m.s. service current does not exceed the continuous rating, when 
run with average service core loss and speed, the motor is ordinarily suitable for the service. 

In some cases, however, it may not have sufficient thermal capacity to avoid excessive 
temperature rises during the periods of heavy load. In such cases a further calculation is 
required, the first step of which is to compute the equivalent voltage which, with the r.m.s. 
current, will produce the average core loss. Having obtained this, determine, as follows, 
the temperature rise due to the r.m.s. service current and equivalent voltage. 

Let t — temperature rise J 

po = PR loss, kw. [■ with r.m.s. service current, and equivalent service voltage. 

pc =* core loss, kw. J 



with continuous load current corresponding to the equivalent 
service voltage. 


Pc *= core loss, kw. 
Then 


Po+Pc . 

t = T -, approximately. 

Po+Pc 


(d) The thermal capacity of a motor is approximately measured by the ratio of the 
electrical loss in kw. at its nominal (one-hour) capacity, to the corresponding maximum 
observable temperature rise during a one hour test starting at ambient temperature. 

(e) Consider any period of peak load and determine the electrical losses in kilowatt-hours 
during that period from the electrical efficiency curve. Find the excess of the above losses 
®ver the losses with r.m.s. service current and equivalent voltage. The excess loss, divided 
by the coefficient of thermal capacity, will equal the extra temperature rise due to the 
peak load. This temperature rise added to that due to the r.m.s. service current, and equiv¬ 
alent voltage, gives the total temperature rise. If the total temperature rise in any such 
period exceeds the safe limit, the motor is not sufficiently powerful for the service. 

(f) If the temperature reached, due to the peak loads, does not exceed the safe limit, the 
motor may yet be unsuitable for the service, as the peak loads may cause excessive sparking 
and dangerous mechanical stresses. It is, therefore, necessary to compare the peak loads 
with the short-period overload capacity. If the peaks are also within the capacity of the 
motor, it may be considered suitable for the given duty-cycle. 





64 


STANDARDS OF THE A. I. E. E. 


CONSTRUCTION 


6601* Standard Height of Trolley Wire on Street and Interurban Rail¬ 
ways.—It is recommended that supporting structures shall be of 
such height that the lowest point of the trolley wire shall be at a 
height of 18 feet (5.5 m.) above the top of rail under conditions of 
maximum sag, unless local conditions prevent. On trackage opera¬ 
ting electric and steam road equipment and at crossings over steam 
roads, it is recommended that the trolley wire shall be not less 
than 21 feet (6.4 m.) above the top of rail, under conditions of max¬ 
imum sag. 

6602 Standard Gage of Third Rails.—The gage of third rails shall be 
not less than 26 inches (66 cm.) and not more than 27 inches (68.6 cm.) 

6603 Standard Elevation of Third Rails.—The elevation of third rails 
shall not be less than 2% inches (7 cm.) and not more than 3^6 
inches (8.9 cm.) 


BIBLIOGRAPHY 


United States 


American Electric Railway (Engineering) Association: Engineer¬ 
ing Manual. 

Association of Railway Electrical Engineers: Standards. 


Foreign 


Engineering Standards Committee of Great Britain: Standardiza¬ 
tion Rules for Electrical Machinery (exclusive of motors for traction 
purposes). Standard Method of Specifying the Resistance of Steel 
Conductor Rails; Standard for Trolley Groove and Wire. 

Verband Deutscher Electrotechniker: Norm alien. 

(5601) A. E. R. A. Standard. 





TRANSFORMERS 


65 


CHAPTER VI. 

STANDARDS FOR TRANSFORMERS AND OTHER 
STATIONARY INDUCTION APPARATUS 

Wherever the General Standards in Chapters II and III apply 
to transformers they are referred to in the following Chapter by 
• cross references. 

Certain rules applying exclusively to railway machinery have, 
for convenience, been placed in Chapter V with cross reference in 
all cases to this Chapter. Rules in Chapter VI apply to railway 
machinery except as they are modified by the rules in Chapter V. 

Note: The work “Transformer” will be used throughout this 
Chapter as an abbreviation of “Transformer or other stationary 
induction apparatus.” 

DEFINITIONS 

Apparatus 

6000 Stationary Induction Apparatus.—For the purpose of these Stand¬ 
ards stationary induction apparatus is defined as electric apparatus 
which changes electric energy to electric energy through the me¬ 
dium of magnetic energy, without mechanical motion. It comprises 
several forms, as defined in §§ 6001 and 6010 to 6015. 

6001 Transformer.—A transformer is a form of stationary induction 
apparatus in which the primary and secondary windings are ordinarily 
insulated one from another. 

6010 Auto-Transformer.—An auto-transformer is one which has a part 
of its turns common to both primary and secondary circuits. 

6011 Voltage-Regulator.—A voltage-regulator is a form of stationary 
induction apparatus which has turns in shunt and turns in series 
with the circuit, so arranged that the voltage ratio of the transforma¬ 
tion, or the phase relation between the circuit-voltages, is variable 
at will. 

6012 Contact Voltage Regulator.—A contact voltage regulator is a 
voltage regulator in which the number of turns in one or both of the 
coils is adjustable. 

6013 Induction Voltage Regulator.—An induction voltage regulator is 
one in which the relative position of the primary and secondary coils 
is adjustable. 

6014 Magneto Voltage Regulator.—A magneto voltage regulator is one 
in which the direction of the magnetic flux with respect to the 
coils is adjustable. 

6016 Reactor.—A reactor is a device used primarily because it possesses 
the property of reactance. Reactors are used in electric circuits for 
purposes of operation, protection or control. 


66 


STANDARDS OF THE A. I. E. E. 


Parts of Apparatus 

6020 High-Voltage and Low-Voltage Winding.—The terms “high 
voltage” and “low voltage” are used to distinguish the winding 
having the greater from that having the lesser number of turns. 

6021 Primary and Secondary Windings.—The term “primary” and 
“secondary” serve to distinguish the windings in regard to energy 
flow, the primary being that which receives the energy from the 
supply circuit, and the secondary that which receives the energy 
by induction from the primary. 

Properties of Apparatus 

6031 Rated Current of a Constant-Potential Transformer.—The rated 
current of a constant-potential transformer is that secondary current 
which, multiplied by the rated-load secondary voltage, gives the 
kv-a. rated output. That is, a transformer of given kv-a. rating 
must be capable of delivering the rated output at rated secondary 
voltage, while the primary impressed voltage is increased to what¬ 
ever value is necessary to give rated secondary voltage. 

6032 Rated Primary Voltage of a Constant-Potential Transformer.— 
The rated primary voltage of a constant-potential transformer is 
the rated secondary voltage multiplied by the turn ratio. 

6033 Ratio of a Transformer.—The ratio of a transformer, unless other¬ 
wise specified, shall be the ratio of the number of turns in the high- 
voltage winding to that in the low-voltage winding; i. e ., the “turn- 
ratio.” 

6034 Voltage Ratio of a Transformer.—The voltage ratio of a trans¬ 
former is the ratio of the r.m.s. primary terminal voltage to the 
r.m.s. secondary terminal voltage, under specified conditions of load. 

6036 Current Ratio of a Transformer.—The current ratio of a current- 
transformer is the ratio of the r.m.s. primary current to the r.m.s. 
secondary current, under specified conditions of load. 

6036 Volt-Ampere Ratio of Transformer.—The volt-ampere ratio, 
which should not be confused with real efficiency, is the ratio of 
the volt-ampere output to the volt-ampere input of a transformer, 
at any given power factor. 

6060* Per Cent Resistance Drop.—The per cent resistance drop in a 
transformer is the ratio of the internal resistance drop at 75°C. to the 
secondary terminal voltage expressed in per cent. 

6061* Per Cent Reactance Drop.—The per cent reactance drop in a 
transformer is the ratio of the internal reactance drop to the second¬ 
ary terminal voltage expressed in per cent. 

6062* Per Cent Impedance Drop.—The per cent impedance drop in a 
transformer is the ratio of the internal impedance drop at 75°C. to 
the secondary terminal voltage expressed in per cent. 

6063 Regulation of Constant-Potential Transformer.—In constant- 
potential transformers, the regulation is the difference between the 


(6050-6051-6052) The internal drop in a transformer is the sum of the primary drop 
(reduced to secondary terms) and the secondary drop. 



TRANSFORMERS 


67 


no-load and rated-load values of the secondary terminal voltage at 
the specified power factor (with constant primary impressed terminal 
voltage) expressed in per cent of the rated-load secondary voltage, 
the primary voltage being adjusted to such a value that the appa¬ 
ratus delivers rated output at rated secondary voltage. See §3390. 

Ambient Temperature.—See §3000. 

RATING 

General 

6201 TABLE 601 


Limiting Observable Temperatures and Temperature Rises for 
Transformers tlsing Class A* Insulation. 



fAir 
Cooled 
and Air 
Blast 

Oil 

Cooled 

Water 

Cooled 

Limiting Observable Tempera¬ 
ture. 

95°C. 

95°C. 

80°C. 

Standard Ambient Tempera¬ 
ture. 

40°C. 

40°C. 

25°C. 

Limiting Observable Tempera¬ 
ture Rise. . 

66°C. 

66°C. 

66°C. 


The temperature of the windings of transformers is always to be 
ascertained by Method 2. 

*For cotton, silk, paper and similar materials when neither treated, impregnated nor 
immersed in oil, the limits of the observable temperature rise shall be 15°C. below the limits 
fixed for these materials when impregnated. 

tFor exceptions in the case of Air Blast Transformers, see §6320 (6). 

6202 Limiting Observable Temperature of Oil (From §2232).—The 
oil in which apparatus is permanently immersed shall, in no part, 
have a temperature, observable by thermometer, in excess of 90°C. 

Permissible Temperatures of Insulations of More Than One 
Class.—See §2104. 

Temperatures of Metallic Parts of Transformers.—See §2116. 

Protection Against Short Circuit.—See §2120. 

Nominal Rating of Railway Substation Transformers.—See §6201. 

Expression of Rating.—See §2202. 

Institute Rating.—See §2204. 

6204* Rating of Protective Reactors.—Protective reactors shall be 
rated by the following characteristics: 

( a ) Kilovolt-amperes absorbed by normal current. 

( b ) Normal current, frequency and line (delta) voltage. 

( c ) Current which the device is required to stand under short 
circuit conditions. 

(6204) Reactors shall be so designed as to be capable of withstanding the sudden 
application, without mechanical injury, of rated current at normal frequency. 

















68 


STANDARDS OF THE A. I. E. E. 


Ambient Temperature of Reference 

Ambient Temperature of Reference for Air.—See §2211. 

Ambient Temperature of Reference for Water-Cooled Transform¬ 
ers.—See §2212. 

Transformers Cooled by Other Means.—See §2213. 

Outdoor Transformers Exposed to Sun’s Rays.—See §2214. 

Altitude Correction 

Altitude.—See §2216. 

8216 Exception to “Altitude”.—See §2216—Water-cooled oil-immersed 
transformers are exempt from this reduction. 

Units in Which Rating Shall be Expressed 

6221 Rating of Transformers.—The rating of transformers shall be 
expressed in kilovolt-amperes (kv-a.) available at the output ter¬ 
minals, at a specified frequency and voltage. 

6223 Rating of Other Stationary Induction Apparatus.—Other sta¬ 
tionary induction apparatus such as auto-transformers, regulators, re¬ 
actors, etc., shall have their ratings appropriately expressed. It is 
also essential to specify the voltage and frequency of the circuits 
on which the apparatus may be used. 

Kinds of Rating 

Continuous Rating.—-See §2220. 

Short-Time Rating.—See §2221. 

Duty-Cycle Operation,—See §2222. 

Standard Short-Time Ratings.—See §2223. 

A. I. E. E. and I. E. C. Ratings.—See §2224. 

Continuous Rating Implied.—See §2226. 

6236 Nominal Ratings.—-Nominal ratings are ratings which do not con¬ 
form with § §2220 and 2221. They are sometimes used for railway 
substation transformers carrying traction loads. Transformers with 
nominal rating shall be capable of operating under the conditions 
enumerated in §6201. 

Rating by Temperature Rise 

Permissible Temperature Rises for Various Ambient Tem¬ 
peratures above Standard.—See §2231 ( d ). 

TESTS 

Ambient Temperature 

Measurement of Ambient Temperatures during Tests of Trans¬ 
formers.—See §2300. 

6300 Measurement of the Ambient Temperature During Tests of 
Water-Cooled Transformers.—The temperature rise of water" 
cooled transformers shall be based entirely upon the temperature of 
the cooling water and it is not necessary to take into account • the 
heat carried off by the air, unless it exceeds the amount specified 
below. If under assumed standard conditions of water at 25° C, 
and air at 40° C, the amount of heat which would be carried off by 


TRANSFORMERS 


69 


the air is 15% or more of the total, the temperature of the cooling 
water, during test, should be maintained within 5° C. of that 
of the surrounding air. Where this is impracticable the am¬ 
bient temperature should be determined from the change in the 
resistance of the windings, using a disconnected transformer, supplied 
with the normal amount of cooling water, until the temperature of 
the windings has become constant. 

Oil Cup.—See §2301. 

Transformer Temperatures 

Temperature Rise for Any Ambient Temperature.—See §2310. 

Correction for the Duration of the Ambient Temperature of the 
Cooling Medium, at the Time of the Heat Test, from the Standard 
Ambient Temperature of Reference.—See §2311. 

6311* Correction for the Deviation of the Ambient Temperature of the 
Cooling Medium, at the Time of the Heat Test of Air-Blast Trans¬ 
formers from the Standard Ambient Temperature of Reference.— 
A correction shall be applied to the observed temperature rise of the 
windings of air-blast transformers due to difference in resistance, 
when the temperature of the ingoing cooling air differs from that of 
the standard of reference. This correction shall be the ratio of the 
inferred absolute ambient temperature of reference to the inferred 
absolute temperature of the ingoing cooling air, i. e. the ratio 
274.5/(234.5 + t)\ where t is the ingoing cooling-air temperature. 

Duration of Temperature Test of Transformers for Continuous 
Service.—See §2312. 

Duration of Temperature Test of Transformer with a Short- 
Time Rating.—See §2313. 

Duration of Temperature Test for Transformer Having More 
Than One Rating.—See §2314. 

Temperature Measurements during Heat Rim.—See §2315. 

6317 Methods of Loading Transformers for Temperature Tests. 

(a) General: Whenever practicable, transformers should be tested 
under conditions that will give losses approximating as nearly as 
possible to those obtained under normal or specified load conditions, 
maintained for the required time The maximum temperature rises 
measured during this test should be considered as the observable 
temperature rises for the given load. See §§2312 to 2314. 

An approved method of making these tests is the loading-back 
method. The principal variations of this method are given in §6317 
(b,) (c) and (d). 

(b) Loading-back with duplicate single-phase transformers: Dupli¬ 
cate single-phase transformers may be tested in banks of two, with 

(6311) Thus, a cooling-air room temperature of 30° C. would correspond to an inferred 
absolute temperature of 264.5° on the scale of copper resistivity, and the correction to 
40* C. (274.5° inferred absolute temperature) would be 274.5/264.5 =» 1.04, making the 
correction factor 1.04; so that an observed temperature rise of say 50° C. at the testing 
ambient temperature of 30° C. would be corrected to 50 X 1.04 = 52° C. this being the 
temperature rise which would have occurred had the test been made with the standard 
ingoing cooling-air temperature of 40° C. 




70 


STANDARDS OF THE A. I. E. E. 


both primary and secondary windings connected in parallel. Normal 
magnetizing voltage should then be applied and the required current 
circulated from an auxiliary source. One transformer can be held 
under normal voltage and current conditions while the other may be 
operating under slightly abnormal conditions. 

(c) Loading-back with one three-phase transformer: One three- 
phase transformer may be tested in a manner similar to §6317 ( b ) 
provided the primary' and secondary windings are each connected in 
delta for the test. Normal three-phase magnetizing voltage should 
be applied and the required current circulated from an auxiliary 
single-phase source. 

( d ) Loading-back with three single-phase transformers : Duplicate 
single-phase transformers may be tested in banks of three in a manner 
similar to that described in §6317 (c), by connecting both primary 
and secondary windings in delta, applying normal three-phase mag¬ 
netizing voltage and- circulating the required current from an auxiliary 
single-phase source. 

(e) Other Methods: Among other methods that have a limited 
application and can be used only under special conditions may be 
mentioned: 

Applying dead load by means of some form of rheostat. 

Running alternately for certain short intervals of time on 
open circuit and then on short-circuit, alternating in this way until 
the transformer reaches a steady temperature. In this test, the volt¬ 
age for the open-circuit interval and the current for the short-circuit 
interval shall be such as to give the same integrated core loss, and 
the same integrated copper loss as in normal operation. 

6320 Method of Temperature Measurement.— (a) Description: The 
temperature of transformer windings shall be measured by their 
increase in resistance, corrected to the instant of shut-down when 
necessary, and by thermometers. Whichever measurement 
yields the higher temperature, that temperature shall be taken as 
the highest observable temperature by Method 2. 

( b ) In the case of air-blast transformers, it is important to have 
the thermometers well distributed and in good contact with the 
coils, and it is especially important to note the temperature near 
the air outlet. In measuring the temperature of air-blast trans¬ 
formers, the air supply shall be shut off immediately at the end of the 
temperature run and the air intake closed to prevent further ad¬ 
mission of cooling air. With the above procedure, the observable 
temperature rise for air-blast transformers may attain a value not 
in excess of 60°C. as determined by thermometer, although it must 
not exceed 55°C. as determined by resistance. 

(c) Temperature Correction for Cooling of Transformer Windings 
after Shut-Down: Since a drop in temperature occurs in a winding 
between the instant of shut-down and the time of measuring the hot 
resistance, a correction shall be applied to the temperature deter¬ 
mined from this measurement so as to obtain, as nearly as practicable, 


TRANSFORMERS 


71 


the temperature at the instant of shut-down. This correction may 
be determined approximately by plotting a time-temperature curve 
with temperatures as ordinates and times' as abscissae and extra¬ 
polating back to the instant of shut-down. 

In cases where successive measurements show increasing tempera¬ 
tures after shut-down the highest value shall be taken. 

In certain cases, however, other correction factors may be applied 
as follows: 

Oil-Immersed Transformers: For the purpose of simplifying the 
application of the rule to transformers when the weight of copper in 
each winding is known and the copper loss as determined by watt¬ 
meter measurement does not exceed 30 watts per lb., the extrapolation 
method has been reduced to the following form which is recom¬ 
mended on account of the greater accuracy obtainable under ordinary 
conditions of testing. The correction in degrees C. shall be the pro¬ 
duct of the watts loss per lb. of copper for each winding multiplied 
by a factor depending upon the time elapsed between shut-down 
and the time of the temperature reading as given in the follow¬ 
ing table: 


Time in Minutes Factor 


1 0.19 

2 0.32 

3 0.43 

4 0.50 


For intermediate times, the value of the factor can be obtained by 
interpolation. 

When the copper loss, measured by wattmeter, does not 
exceed 7 watts per lb. an arbitrary correction of one degree per 
minute may be used provided the time elapsed between the instant 
of shut-down and the measurement of the hot resistance does not 
exceed 4 minutes. 

For determining the copper loss in watts per lb., the total loss in 
both windings as measured by the wattmeter should be apportioned 
between the high and low voltage windings in the same ratio as their 
respective PR losses. 

Air-Blast Transformers: An arbitrary correction of one degree 
per minute may be used provided the time elapsed between the 
instant of shut-down and the measurement of the hot resistance does 
not exceed four minutes. 

( d) Covering of Thermometers: Thermometers used for taking 
the temperature of air-cooled or air-blast transformers shall have 
their bulbs covered for protection from air currents. This shall be 
done by felt pads, approximately 4 cm. x 5 cm. (1 1/2 in. x 2 in.) and 








72 


STANDARDS OF THE A. I. E. E. 


3 mm. (1/8 in.) thick, except that where pads are inconvenient, as 
in ventilating ducts between coils, grooved wooden sticks may¬ 
be used. 

Temperature Coefficient of Copper.—See §2321. 

Efficiency 

Efficiencies Recognized.—See § 2331. 

Normal Conditions for Efficiency Tests.—See § 2332. 

Direct Measurement of Efficiency.—See § 2333. 

6334 Classification of Losses.—(a) General : Losses are classified as 
shown below. 

(b) No-Load Losses : No-load losses include the core loss, the 
PR loss due to the exciting current and the dielectric loss in the 
insulation. 

(c) Load Losses : Load losses include PR losses, and stray load- 
losses due to eddy-currents caused by fluxes varying with load. 

6336 Losses to be Considered in Transformers.—Conventional effi¬ 
ciencies shall be based upon the losses listed in §6334 and these 
losses shall be measured as specified in §§6336 and 6337. 

6336 No-Load Losses.—The no-load losses shall be measured with 
open secondary circuit at the rated frequency, and with an applied 
primary voltage giving the rated secondary voltage plus the I R 
drop which occurs in the secondary under rated load conditions. 

6337 Load Losses.—The load losses include PR and stray load-losses* 
They shall be measured by applying a primary voltage, at rated 
frequency, sufficient to produce rated load current in the wind¬ 
ings, with the secondary windings short-circuited. 

Wave Shape 

Standard Wave Shape.—See § 2340. 

Tests of Dielectric Strength 

Condition of Transformers to be Tested.—See §2360. 

Where High Voltage Tests are to be Made.—See §2361. 

Temperature at which High Voltage Tests are to be Made.— 
See §2362. 

Points of Application of Voltage.—See §2363. 

Frequency and Wave Form of Test Voltage.—See §2364. 

Duration of Application of Test Voltage.—See §2366. 

6366 Standard Test Voltage.—(From §2366.) General : The standard 
test voltage for all machines, except as otherwise specified, shall be 
twice the normal voltage of the circuit to which the machine is 
connected plus 1000 volts. See exception §6361. 

6360 Transformers for Star Connection.—Transformers which may be 
used in star connection on three-phase circuits shall be tested on 
the basis of the line to line voltage for which they are rated. See 
§6361-f. 

6361* Exceptions to Standard Test Voltage Given in Section 6366.— 

(a) Distributing Transformers : Transformers for primary pres. 


TRANSFORMERS 


73 


sures from 550 to 4500 volts, the secondaries of which are directly 
connected to consumers’ circuits and commonly known as distributing 
transformers, shall be tested with 10,000 volts from primary to core 
and secondary combined. The secondary windings shall be tested 
with twice their normal voltage plus 1000 volts. 

( b ) Auto-Transformers: Auto-transformers used for starting 
purposes, shall be tested with the same voltage as the test voltage of 
the apparatus to which they are connected. 

(c) Household Devices: Transformers taking not over 660 watts 
and intended solely for operation on supply circuits not exceeding 
275 volts, shall be tested with 900 volts. 

* (d) Transformers for Use on Circuits of 25 Volts or Lower : Trans¬ 
formers for use on circuits of 25 volts or lower, such as bell-ringing 
apparatus, shall be tested with 500 volts. 

(e) Alternating Current Transformers Connected to Permanently 
Grounded Single Phase Systems, for use on Permanently Grounded 
Circuits of more than 300 Volts: Transformers used under these 
conditions shall be tested with 2.73 times the voltage of the circuit 
to ground plus 1000 volts. This does not refer to three-phase 
transformers operating with grounded neutral. 

(f) Transformers to be used on star-connected three-phase 
circuits: Transformers which may be used in star connection 
on three-phase circuits shall have the line to line (as distinguished 
from line to neutral) voltage of the circuits on which they may be 
used indicated on the rating plate and the test shall be based on 
the line to line voltage. See §6360. 

(g) Protective Reactors : Protective reactors shall be tested from 
conductors to ground with 2000 volts plus 2^£ times the line voltage. 

6362* Testing Transformers by Induced Voltage.—Under certain con¬ 
ditions it is permissible to test transformers by inducing the required 
voltage in their windings in place of using a separate testing trans¬ 
former. By “required voltage” is meant a voltage such that the 
line end of the windings shall receive a test to ground equal to that 
required by the general rules. 

6363 Transformers with Graded Insulation.—Where transformers have 
graded insulation they shall be so marked. They shall be tested by 
inducing the required test voltage in the transformer and connecting 
the successive line leads to ground. 

Transformer windings permanently grounded within the trans¬ 
former shall be tested by inducing the required test voltage in such 
windings. See §6361. 

Use of Voltmeter and Spark-gaps in Dielectric Tests.—See §2359. 

Use of Spark-gap with Transformers of Low Capacitance.—See 
§2360. 

Use of Spark-gap with Transformers of High Capacitance.—See 
§2361. __ 

(6361-d) This rule does not include bell-ringing transformers of ratio 125 to 6 volts. 

(6362) This test can be made by connecting the windings of two or more transformers 
in series, with one end of the series grounded and a voltage impressed such as will give the 
test from the free end to ground required by the above rule. 




74 


STANDARDS OF THE A. I. E. E. 


Measurements with Voltmeter.—See §2362. 
Measurements with Spark-gap.—See §2363. 

Regulation 

Conditions for Tests of Regulation.—See §2390. 


6390 Conditions for Tests of Regulation.—(a) Frequency: The reg¬ 
ulation of transformers is to be determined at constant frequency. 

(b) Power Factor: In transformers, the power factor of the load 
to which the regulation refers should be specified. Unless otherwise 
specified, it shall be understood as referring to non-inductive load, 
that is, to a load in which the current is in phase with the e.m.f. at 
the output side of the transformer. See §2390. 

6391* Tests and Computation of Regulation.—*(a) Method I. By 
Loading: The regulation of a constant potential transformer can 
be determined by loading the transformer and measuring the change 
in voltage with change in load, at the specified power factor. 

(b) Method II. From Impedance Watts and Volts : The regula¬ 
tion of a constant potential transformer for any specified load and 
power factor can be computed from the measured impedance watts 
and impedance volts as follows: 

Let: 

P = impedance watts, as measured in the short-circuit test and 
corrected to 75°C. 

E z — impedance volts, as measured in the short-circuit test. 
IX = Reactance Drop in Volts. 

7 = Rated Primary Current. 

E — Rated Primary Voltage. 

q r = per cent drop in phase with current. 

q x — per cent drop in quadrature with current. 


IX 


-V*_ 


q r = 100 


El 


q x = 100 


I X 
E 


Then— 

For unity power factor, we have approximately, 

2 


Per cent regulation — q r -f 


2 * 


200 


For inductive loads of power-factor m and reactive-factor n, 

( mq x —nq r ) 2 


Per cent regulation — m q r -f- n q x -\- 


200 


(6391 a) This method is not generally applicable for shop tests, particularly on large 
transformers. 









TRANSFORMERS 


75 


CONSTRUCTION 


Rating Plates 

Marking of Rating Plates.—See §2401. 

Transformer Connections 

(These rules do not apply to auto-transformers) 

General 

6402* Scope.—These rules specify the markings of leads brought out of 
the case but not the markings of winding terminals inside of the case, 
except that these terminals shall be marked with numbers in any 
manner that will permit of convenient reference and that cannot be 
confused with the markings of the leads brought out of the case. 

TRANSFORMER LEAD MARKINGS SINGLE PHASE TRANSFORMERS 




Simple Hi.jh and Low-Voltage Windings Without Taps 



FIG- 6-5 FIG. 6-4 

Simple High and Low-Voltage Wincirgs With Taps 


H 1 


H 2 


H 2 


H 3 



t/) 

FIG. 6-3 

Series Multiple Low-Voltage Winding 
Without Taps 



FIG. 6-6 

Series Multiple Low-Voltage Winding 
With Taps 


Note :—The above figures illustrate the application of the rules on lead markings to 
transformers having subtractive and additive polarity. 

(6402) It is recognized that special cases will arise from time to time that these rules 
will not cover and that it would be very difficult to cover by any set of general rules. 

















76 


STANDARDS OF THE A. I. E. E. 


6403* Markings of Leads.— *(a) General: The leads shall be dis¬ 
tinguished from one another by marking each lead with a capital 
letter followed by a number. The letters to be used are: H for 
high voltage leads, X for low voltage leads and Y for tertiary winding 
leads. The numbers to be used are 1, 2, 3, etc. 

*(b) Neutral Lead: A neutral lead shall be marked with the 
proper letter followed by 0, e.g., HO, XO. 

6404 Diagrammatic Sketch of Connections.—The manufacturer shall 
furnish with each transformer a complete diagrammatic sketch 
showing the leads and internal connections and their markings and 
the voltages obtainable with the various connections. 

This sketch should preferably be on a metal plate attached to the 
transformer case. 

Single-Phase Transformers 

6405 Order of Numbering Leads in any Winding.—The leads of any 
winding (high-voltage, low-voltage or tertiary) brought out of case 
shall be numbered 1, 2, 3, 4, 5, etc., the lowest and highest numbers 
marking the full winding and the intermediate numbers marking 
fractions of winding or taps. All numbers shall be so applied that 
the potential difference from any lead having a lower number toward 
any lead having a higher number shall have the same sign at any 
instant. 

If a winding is divided into two or more parts for series parallel 
connections, and the leads of these parts are brought out of case, 
the above rule shall apply for the series connection with the addi¬ 
tion that the leads of each portion of winding shall be given consecu¬ 
tive numbers. See Figs. 6-5 and 6-6. 

6406 Relation of Order of Numbering Leads of Different Windings. 

The numbering of the high-voltage and low-voltage leads shall be so 
applied that when H\ and Xi are connected together and voltage 
applied to the transformer, the voltage between the highest numbered 
H lead and the highest numbered X lead shall be less than the volt¬ 
age of the full high-voltage winding. 

The same relation shall apply between high-voltage and tertiary 
and low-voltage and tertiary winding. 

6407 Polarity.—When leads are marked in accordance with the above 

rules, the polarity of a transformer is 

Subtractive when Hi and X\ are adjacent. See Figs. 6-1, 6-3 and 6-5. 

(6403-a) By “tertiary winding” is meant a third winding that, compared with both of 
the other two windings, has smaller kv-a. rating than either or, if the kv-a. rating is the 
same as one or both of the other two, has lower voltage. E. g., if a transformer has three 
separate windings, one for 1000 kv-a., 33,000 volts, one for 600 kv-a., 650 volts and one for 
400 kv-a. 6,600 volts, the 400 kv-a. winding is the tertiary winding; or, if a transformer 
has three separate windings each with a capacity of 1,000 kv-a., and with voltages of 
33,000, 6600 and 550 respectively, the 550 volt winding is the tertiary winding. 

According to this definition neither one of two similar windings arranged for series- 
parallel connection is to be classed as a tertiary winding. 

(6403-b) A lead brought out from the middle of a winding for some other use, than that 
of neutral lead, e.g., a 50 per cent starting tap, shall be marked as a tap lead. 




TRANSFORMERS 


77 


Additive when Hi is diagonally located with respect to X\. See 
Figs. 6-2, 6-4 and 6-6. 

6408 Location of H\ Lead.—To simplify the work of connecting trans¬ 
formers in parallel it is recommended that the H\ lead shall be brought 
out on the right hand side of the case, facing high-voltage side of the 
case. 


transformer lead markings and voltage vector diagrams for 

THE USUAL THREE PHASE TRANSFORMER CONNECTIONS 



Note:—T he above figures are included to illustrate the method of marking trans* 
former leads that are brought out of the case and are not intended to standardize con¬ 
nections, vector diagrams or polarity. 

























78 


STANDARDS OF THE A. I. E. E. 


6409* Parallel Operation. —Transformers having leads marked m accord¬ 
ance with these rules may be operated in parallel by connecting 
similarly marked leads together, provided their ratio, voltages, 
resistances and reactances are such as to permit parallel operation. 

Three-Phase Transformers 

6410 Marking of Full Winding Leads. —The three high-voltage leads and 
the three low-voltage leads which connect to the full-phase wind¬ 
ings, shall be marked Hi, H 2 , H 3 , and Ji, X 2 , Xz- The full-phase 
winding of a tertiary winding shall be marked Y 1 , ¥ 2 , Y 3 , 


TRANSFORMER LEAD MARKINGS AND VOLTAGE VECTOR DIAGRAMS FOR 
THE USUAL SIX-PHASE TRANSFORMER CONNECTIONS 



Note: —The above figures are included to illustrate the method of marking trans¬ 
former leads that are brought out of the case and are not intended to standardize con¬ 
nections, vector diagrams or polarity. 


6411* Relation between High-Voltage and Low-Voltage Windings.— 

(a) General: The markings shall be so applied that if the phase 
sequence of voltage on the high voltage side is in the time order Hi, 
H 2 , Hz it is in the time order of, X\, X 2 , Xz on the low-voltage side 
and Yi, Y 2 , Yz for a tertiary winding. 

(6409) In some cases design may be such as to permit parallel operation, although due 
to the difference in the number of tap leads, the leads to be connected together may not 
have the same number. 





























TRANSFORMERS 


79 


*(&) Angular Displacement: In order that the markings of lead 
connections between phases shall indicate definite phase relations, 
the 3 r shall be made in accordance with one of the three three-phase 
groups as shown. The angular displacement between the high- 
voltage and low-voltage windings is the angle in each of the voltage 
vector , diagrams (Figs. 6-7 to 6-14 inclusive) between the lines 
passing from its neutral point through H\ and X\ respectively. 

6412 Tap Leads.— {a) General: Where tap leads are brought out of the 
case (neutral lead excepted) they shall be marked with the proper 
letter followed by the numbers 4, 7, etc., for one phase, 5, 8, etc., for 
another phase and 6, 9, etc., for the third phase. See Fig 6-15. 

( b ) Delta Connection: The order of numbering tap leads shall be 
as follows: 4, 7, etc., from lead 1 toward lead 2; 5, 8, etc., from lead 2 
toward lead 3; and 6, 9, etc., from lead 3 toward lead 1. See Fig. 
6-15. 

(c) Star Connection: The order of numbering tap leads shall be 
as follows': 4, 7, etc., from lead 1 towards neutral; 5, 8, etc., from lead 
2 towards neutral; and 6, 9, etc., from lead 3 towards neutral. See 
Fig. 6-15. 

6413 Interphase Connection made Outside of Case.—Where the inter¬ 
phase connections are made outside of case, the leads shall be marked 
with the proper letter followed by the numbers 1, 4, 7, 10, etc., for 
one phase; 2, 5, 8, 11, etc., for the second phase; and 3, 6, 9, 12, etc., 
for the third phase. 

The markings shall be so applied that when a star connection is 
made by joining together the highest numbered leads of each phase, 
all rules here given, excepting §6403 (b) apply. 

6414* Parallel Operation.—Transformers having leads marked in 
accordance with these rules may be operated in parallel by connecting 
similarly marked leads together provided their angular displacements 
are the same and provided also their ratios, voltages, resistances, and 
reactances are such as to permit parallel operation. 

6415 Location of HI Lead.—To simplify the work of connecting trans¬ 
formers in parallel it is recommended that the H 1 lead shall be 
brought out on the right hand side of the case, facing the high- 
voltage side of the case. 

Three-Phase to Six-Phase Transformers. 

6416 Rules that are Applicable for Three-Phase Transformers.—Sections 
6411 (b) and 6413 shall apply to throe-phase to six-phase transformers. 

(6411-b) Any three phase transformer having a delta Y connection may be represented 
by voltage vector diagram either in accordance with Fig. 6-11 or Fig. 6-13. Any three 
phase transformer having Y delta connection may be represented by voltage vector diagram 
either in accordance with Fig. 6-12 or Fig. 6-14. Since these voltage vector diagrams are 
equivalent, it is recommended that the terminal markings for three phase transformers 
having delta Y connection be always made in accordance with Fig. 6-11 and that the 
terminal markings for three phase transformers having Y delta connection be always made 
in accordance with Fig. 6 12. 

(6414) In some cases designs may be such as to permit parallel operation although, due 
to a difference in the number of tap leads, the leads to be connected together are not simil¬ 
arly marked. 



80 


STANDARDS OF THE A. I. E. E. 


Rules 6410 and 6412 shall apply to three-phase windings but not to 
six-phase windings. 

6417 Markings of Six-Phase Leads.—The six leads which connect to 
the full-phase windings shall be marked XI, X2, X3, X4, X5, X6. 
See Figs. 6-16 to 6-19 inclusive. 

6418 Relation between Three-Phase and Six-Phase Windings.— (a) 

General: The markings shall be so applied that if the phase sequence 
of voltage on the three-phase side is in the time order HI, H2, 
H3, it is in the time order of XI, X2, X3, X4, X5, X6 on the six- 
phase side. 

(b) Angular Displacement: In order that the markings of lead 
connections between phases shall indicate definite phase relations, 
they shall be made in accordance with one of the four six-phase 
groups shown in Figs. 6-16 to 6-19 inclusive. The angular displacement 
between the high-voltage and low-voltage windings is the angle in 
each of the voltage vector diagrams from its neutral through HI and 
XI respectively. 

6419* Tap Leads.—( a) General: Where tap leads from low-voltage wind¬ 
ings are brought out of the case (neutral lead excepted), they shall 
be marked as follows: 

(b) Diametrical Connection: Diametrical connection tap leads 
shall be marked from the two ends of each phase winding towards the 
middle or neutral point in the following order; X7, X13, etc., from 
XI towards neutral; X8, X14, etc., from X2 towards neutral; X9, 
X15, etc., from X3 towards neutral; X10, X16, etc., from X4 towards 
neutral; Xll, X17, etc., from X5 towards neutral; X12, X18, etc., 
from X6 towards neutral. See Fig. 6-20. 

A tap from the middle point of any phase winding, not intended 
as a neutral, shall be given a number determined by counting from 
XI, X2 or X3 and not from X4, X5, or X6‘, e.g., if the only taps 
brought out are 50 per cent starting taps, they shall be numbered 
X7, X8, and X9. 

*(c) Double Delta Connection: Tap leads shall be marked in the 
following order; X7, X13, etc., from XI towards X3\ X8, X14, etc., 
from X2 towards X4\ X9, X15, etc., from X3 towards X5\ X10, 
X16, etc., from X4 towards X6\ Xll, X17, etc., from X5 towards 
XT, X12, X18, etc., from X6 towards X2. See Fig. 6-21. 

BIBLIOGRAPHY 
United States 

Electric Power Club: Standardization Rules. 

National Board of Fire Underwriters: National Electrical Code. 
National Electric Light Association: Committee Reports. 

Foreign 

Associazone Elettrotecnica Italiana: Norme per 1’ordinazione e il 

collando delle Macchine Elettriche. 

(6419-c) For starting purposes it is generally customary to bring out only two taps from 

one delta and start three-phase. 




TRANSFORMERS 


81 


British Electrical and Allied Manufacturers’ Association: Reports 
British Engineering Standards Association: British Standardiza¬ 
tion Rules for Electrical Machinery (except motors for traction 
purposes). 

Socidte Internationale des Electriciens: Bulletins. 

Union des Syndicats de 1’ Electricite: Instructions g6n6rales pour 
la Fourniture et la Reception des Machines 61ectriques. 

Verband Deutscher Elektro-techniker: Normalien, Vorschriften 
und Leitzsatze. 

International 

International Electrotechnical Commission: Rating of Electrical 
Machinery. 


82 


STANDARDS OF THE * 4 . I. E. E. 


CHAPTER VII. 

STANDARDS FOR SWITCHING, CONTROL AND 
PROTECTIVE APPARATUS 

The A. I. E. E. Standards for Switching Control and Protective Appar¬ 
atus are the General Standards shown in Chapters II and III and the 
Standards in other Chapters which are applicable to the devices involved, 
together with the modifications and extensions given in this Chapter. 

DEFINITIONS 

Devices 

7000* Switching and Control Apparatus.—For the purpose of these 
Standardization Rules switching and control apparatus is defined as 
electric apparatus whose function is primarily to control or protect 
in some predetermined manner electric apparatus to which it is con¬ 
nected. 

7001 Switch.—A switch is a device for making, breaking or changing 
the connections in an electric circuit. 

7002 Master-Switch.—A master-switch is a switch which serves to 
govern the operation of contactors and auxiliary devices of an electric 
controller. 

7003 Control Switch.—A control switch is a switch for controlling 
electrically-operated switches and circuit breakers. 

7004 Auxiliary Switch.—An auxiliary switch is a switch actuated by 
some main device, for signalling, interlocking, etc. 

7005 Circuit-Breaker.—A circuit-breaker is a device (other than a fuse) 
constructed primarily for the interruption of a circuit under infre¬ 
quent abnormal conditions. 

7006 Contactor.—A contactor is a device for repeatedly establishing and 
interrupting an electric circuit under normal conditions. 

7007* Electric Controller.—An electric controller is a device, or group 
of devices, which is designed to control in some predetermined 
manner the operation of the apparatus to which it is connected. 

7008* Motorstarter.—A motorstarter is an electric controller designed 
for accelerating a motor to normal speed in one direction of rotation. 

7009 Automatic Motorstarter.—An automatic motorstarter is a motor¬ 
starter designed to automatically control the acceleration of a motor. 

(7000) The “National Electrical Cole” of the National Fire Protection Association 
deals with certain circuit breakers up to 550 volts rati ig and switches an 1 fuses up to 
600 volts rating fuses. 

(7007) A switch (see §7001) should not be called a controller. 

(7003) A device designed for starting a motor in either direction' of rotation is called 
a controller (see §7007). 



SWITCHING, CONTROL AND PROTECTIVE APPARATUS 83 


7010 Auto-Transformer Motorstarter. —An auto-transformer motor- 
starter is a motor-starter having an auto-transformer to furnish a 
reduced voltage for starting. The device includes the necessary 
switching mechanism, and is frequently called a Compensator or 
Auto-Starter. 

7016* Fuse. —A fuse is an element designed to melt or dissipate at a 
predetermined current value, and intended to protect against 
abnormal conditions of current. 

7016 Relay •—A relay is a device by means of which contacts in one 
circuit are operated by change in conditions in the same or other 
circuits. 

7018 Rheostat. —A rheostat is a resistor which is provided with means 
for readily varying its resistance. See §3064. 

7019 Protective Reactor.^-A protective reactor (See §3078) is a device 
for protecting circuits by limiting the current flow and localizing 
the disturbance under short circuit conditions. 

• 7020* Lightning Arrester. —A lightning arrester is a device for protecting 
circuits and apparatus against lightning or other abnormal potential 
rises of short duration. 

7021 Under-Voltage or Low-Voltage Release Switching and Control 
Apparatus. —Under-voltage or low-voltage release switching and 
control apparatus is apparatus which, on the reduction or failure of 
voltage, operates to cause the interruption of power to the main 
circuit, but which does not prevent the re-establishment of the main 
circuit on return of voltage. 

7022 Under-voltage or Low-Voltage Protection Switching and Control 
Apparatus. —-Under-voltage or low-voltage protection switching and 
control apparatus is apparatus which, on the reduction or failure of 
voltage, operates to cause and maintain the interruption of power to 
the main circuit. 

7023 Phase-Failure Protection Switching and Control Apparatus.— 

Phase-failure protection switching and control apparatus is apparatus 
which, on the failure of power in one wire of a polyphase circuit, 
operates to cause and maintain the interruption of power on the 
circuit. 

7024 Phase-Reversal Protection Switching and Control Apparatus.— 

Phase-reversal protection switching and control apparatus is appara- 

(7015) Any terminals, tubes, etc., integral with this element are included as part of the 
fuse. 

Puses may be divided into two classes: 

(a) Those designed to protect the circuit and apparatus both against short-circuit and 
against definite amounts of overload (e. g. fuses of the National Electric Code which open 
on 25 per cent overload.) 

(b) Those designed to protect the system only against short circuits; ( e . g. expulsion 
fuses, which blow at several times the current which they are designed to carry continu¬ 
ously). The line separating these two classes is not definitely fixed. 

(7020) Lightning arresters may be divided into two classes: 

(a) Those intended to discharge for a very short time. 

(b) Those intended to discharge tor a period of several minutes. 



84 


STANDARDS OF THE A. I. E. E. 


tus which, on the reversal of the phase relations in a polyphase cir¬ 
cuit, operates to cause and maintain the interruption of power on 
the circuit. 

Characteristics of Devices 

7030 “Air” as a Prefix.—The prefix “air” applied to a device which 
interrupts an electric circuit indicates that the interruption occurs in 
air. 

.7031 “Oil” as a Prefix.—The prefix “oil” applied to a device which 
interrupts an electric circuit indicates that the interruption occurs in 
oil. 

7032 Fume-Resisting.—Fume-resisting switching and control apparatus 
is apparatus so constructed that it will not be readily injured by the 
specified fumes. 

7033* Drip-Proof.—Drip-proof switching and control apparatus is 
apparatus so protected as to exclude falling moisture or dirt. 

7034 Dust-Proof.—Dust-proof switching and control apparatus is 
apparatus so constructed or protected that the accumulation of dust 
within or without the device will not interfere with its successful 
operation. 

7036 Dust-Tight.—Dust-tight switching and control apparatus is 
apparatus so constructed that the dust will not enter the enclosing 
case. 

7036 Explosion-Proof.—Explosion-proof switching and control appara¬ 
tus is apparatus so constructed that explosions of gas within the 
casing will not injure it or ignite inflammable gas outside it. 

7037 Gas-Proof.—Gas-proof switching and control apparatus is appara¬ 
tus so constructed or protected that the specified gas will not inter¬ 
fere with its successful operation. 

7038 Gas-Tight.—Gas-tight switching and control apparatus is appara¬ 
tus so constructed that the specified gas will not enter the enclosing 
case. 

7039 Moisture-Resisting.—Moisture-resisting switching. and control 
apparatus is apparatus so constructed or treated that it will not be 
readily injured by moisture. (Such apparatus shall be capable of 
operating in a very humid atmosphere, such as found in mines, 
evaporating rooms, etc.). 

7040 Splash-Proof.—Splash-prdbf switching and control apparatus is 

apparatus so constructed or protected that external splashing will 
not interfere with its successful operation. » 

7041 Submersible.—Submersible switching and control apparatus is 
apparatus so constructed that it will operate successfully when 
submerged in water under specified conditions of pressure and time. 

7042 Sleet-Proof.—Sleet-proof switching and control apparatus is 
apparatus so constructed or protected that the accumulation of 
sleet will not interfere with its successful operation. 

(7033) Drip-proof apparatus may be either open or semi-enclosed, if it is provided with 

suitable protection integral with the apparatus, or so enclosed as to exclude effectively 

falling solid or liquid material. 



SWITCHING , CONTROL AND PROTECTIVE APPARATUS 85 


Parts of Devices 

7050 Conducting Parts. —Conducting parts of switching and control 
apparatus are those designed to carry current or which are con- 
ductively connected therewith. 

7061 Contact. —A contact is a surface common to two conducting parts, 
united by pressure, for the purpose of carrying current. 

7062 Magnet Brake. —A magnet brake is a friction brake controlled by 
electro-magnetic means. 

7063 Grounded Parts. —Grounded parts are those parts which may be 
considered to have the same potential as the earth. 

Properties of Devices. 

7060 Interrupting Rating. —Interrupting (breaking or rupturing) 
rating is a rating based upon the r. m. s. current at normal voltage 
which the device can interrupt under prescribed conditions at stated 
intervals a specified number of times. 

OPERATION 
Temperature Limits 

7101* Circuit Breakers, Relays and Switches. —The maximum observ¬ 
able temperature rises of the various parts of circuit breakers, relays 
and switches shall not exceed the following limits for ambient 
temperatures up to and including but not greater than 40°C. See 


§7301. 

Contacts in air, when clean and bright. 30°C. 

Oil and contacts therein. 30°C. 

Coils, if insulation is of unimpregnated fibrous material.... 35°C. 
Coils, if insulation is of fibrous material treated to with¬ 
stand heat. 50°C. 

Coils, if insulation is of asbestos, mica or similar heat resist¬ 
ing material. 70°C. 


Coils on which a thermometer can be applied directly to the sur¬ 
face of the bare winding, such as those having bare edgewise strip 
conductors, shall be allowed 10°C. higher maximum observable 
temperature rise than permitted above for each kind of insulation. 

Other parts: All other parts than those whose temperature affects 
the temperature of the insulating material may be operated at such 
temperatures as shall not be injurious in any other respect. 

7102 Magnetic Contactors. —The maximum observable temperature 
rises of the various parts of magnetic contactors shall not exceed the 
following limits for ambient temperatures up to and including but 
not greater than 40° C. See §7302. 

Laminated contacts. 65°C. 

Operating coils. 70°C. 

Solid contacts. 100°C. 

(7101) The Institute calls attention to the inherent decrease in current which can 
be carried by switch and circuit breaker contacts in air, due to oxidization of the contact 
surfaces. The rating of air switches and circuit-breakers is, therefore, based on sufficient 
maintenance to keep the temperature rise within the specified limits. Relays which form 
part of controllers are to have the temperature limits specified in §7102. 










86 


STANDARDS OF THE A. I. E. E. 


Current-carrying parts ipsulated with asbestos or other 

fireproof material. 150°C. 

7106* Fuses. —The maximum observable temperature rise of coils or 
windings, measured by thermometer, shall not exceed the following 
limits for ambient temperatures up to and including but not greater 


than 40°C. 

If insulation is of unimpregnated fibrous material. 35°C. 

If insulation is of fibrous material treated to withstand heat 50°C. 
If insulation is of asbestos, mica or similar heat resisting 

material with a cotton binder. 70°C. 


7106 Cast Grid Resistors. —The maximum observable temperature 
rises of cast grids used as resistors shall not exceed 350°C. for ambient 
temperatures up to and including but not greater than 40°C. 

RATING 

Expression of Rating 

7201 Rating of Circuit Breakers and Switches. —The rating of a circuit 

breaker or switch shall include the following items: 

(a) the normal r. m. s. current which it is designed to carry. 

(b) the normal r. m. s. pressure (voltage) of the circuit on which 
it is intended to operate. 

(c) the normal frequency of the current. 

(d) the interrupting rating of the device. See §7060. 

7202 Continuous Current-Carrying Capacity of Fuses.—Fuses shall 
be so constructed that they will carry continuously 110 per cent 
of their rated current. 

7206 Rating of Lightning Arresters. —The rating of a lightning arrester 
shall be the voltage of the circuit on which it is to be used. 

TESTS 
Heat Tests 

7301 Circuit-Breakers, Relays and Switches. —The rated current of 
circuit-breakers, relays and switches at rated frequency shall be 
applied continuously until the temperature becomes constant. The 
temperature rises measured by thermometer shall not exceed the lim¬ 
its specified in §7101. 

7302 Magnetic Contactors. —The rated current of magnetic contactors 
at rated frequencies shall be applied continuously or until the tem¬ 
perature becomes constant when continuous duty is specified. It 
shall be applied for the specified length of time when given a short 
time rating. The temperature rises measured by thermometer shall 
not exceed the limits specified in §7102. 

Tests of Dielectric Strength 

7323* Standard Test Voltage.— {a) Apparatus rated at 600 volts or lessi 
The standard test voltage for all switching and control apparatus 

(7105) Coils or windings such as accompany fuses of the magnetic blow-out type. 

(7323) This assumes a precipitation of l/10th inch (2.54 mm.) per minute at an angle 

of 45° from the perpendicular with water having a resistivity as low as 7000 ohm-centi¬ 
meters. 







SWITCHING , CONTROL AND PROTECTIVE APPARATUS 87 


rated at 600 volts or less shall be twice the normal voltage of the 
circuit to which the apparatus is to be connected plus 1000 volts. 

(b) Apparatus rated above 600 volts: Apparatus rated above 600 
volts shall be tested at 234 times rated voltage, plus 2000 volts, 
at a specified altitude. 

*As a supplementary test, devices for outdoor use should be capable 
of withstanding for 10 seconds a dielectric wet test at twice rated 
voltage plus 1000 volts. 

(c) Auto-Transformers for Motor starters: Auto-transformers for 
motorstarters shall be tested with the same voltage as the test voltage 
of the apparatus to which they are to be connected. 

Tests of Lightning Arresters. 

7371 Resistance. —The resistance of the arrester at double potential 
and also at normal pbtential, shall be determined by observing the 
discharge currents through the arrester. 

7372 Arrester with Gap. —In the case of any arrester using a gap, a test 
shall be made of the spark potential on either direct-current or 60 
cycle a-c. excitation. 

7373 Equivalent Sphere Gap. —The equivalent sphere gap under dis¬ 
ruptive discharge shall be measured, using a considerable quantity 
of electricity. 

7374 Continuous Surges. —The endurance of the arrester to continu¬ 
ous surges shall be tested. 

7376 Dielectric Strength. —See §§ 2365 and 7323. 

BIBLIOGRAPHY 
United States 

Electric Power Club: Standardization Rules. 

National Board of Fire Underwriters: National Electrical Code. 
National Electric Light Association: Committee Reports. 

Foreign 

British Engineering Standards Association: Specifications for 

Starters for Electric Motors. 


88 


STANDARDS OF THE A. I. E. E. 


CHAPTER VIII. 

STANDARDS FOR METERS, INSTRUMENTS AND 
INSTRUMENT TRANSFORMERS 

The A. I E. E. Standards for Meters, Instruments and Instrument 
Transformers are the General Standards shown in Chapters II and III, 
and the Standards in other Chapters which are applicable to the devices 
involved, together with the modifications and extensions given in this 
Chapter. 


DEFINITIONS. 

8000* Meter. A meter is a device which registers through a totalizing 
mechanism, the integral, with respect to time, of the electrical 
quantity to which it responds. (This definition does not preclude 
the general use of “meter” as a suffix or in compound words, to mean 
a “measuring device.”) 

8001* Instrument. An instrument is a device which indicates or records 
the present value of the quantity under observation. 

8002 General Nomenclature. In general, the names of meters and 
instruments are self-defining. The following names are preferred 
to others sometimes used for the same devices: Reactive-Factor 
Meter, Power-Factor Meter, Watthour Meter, Reactive Volt- 
Ammeter (or Reactive Volt-Ampere Indicator) etc. 

8003 Recording Instruments. Recording ammeters, voltmeters, watt¬ 
meters, etc. are instruments which record graphically, upon time 

. charts, the values of the quantities they measure. 

8004 Crest Voltmeter. A crest voltmeter is a voltmeter depending for 
its indications upon the crest, or maximum value of the voltage of the 
system to which it is connected. Crest voltmeters shall be marked 
in true crest volts and also in the r. m. s. value of the sinusoidal wave 
having the same crest value. (See §2362.) 

8006 Synchronoscope (also called a Synchroscope or Synchronism 
Indicator). A synchronoscope is a device which indicates synchron¬ 
ism between two machines, and in addition shows whether the in¬ 
coming machine is fast or slow. 

8006 Line-Drop Voltmeter Compensator. A line-drop voltmeter com¬ 
pensator is a device used in connection with a voltmeter which causes 
the latter to indicate the voltage at some distant point of the circuit. 

(8000 & 8001) While the word “instrument” is a general term which may properly 
include indicating, integrating and recording devices, there is a tendency to restrict its 
use to indicating devices and to, recording (graphic or curve drawing) devices. Integrating 
devices are then denoted by the word “meter.” This distinction gives rise to the above 
general definitions. 



METERS AND INSTRUMENTS 


89 


8007 Demand-Meter, (a) General : A demand-meter is a device 
which indicates or records the demand or maximum demand. In 
practise, two types are recognized. See §§ 3454,3458, 3460 and 3464. 

(&) Integrated-Demand-Meter: An integrated-demand-meter is a 
demand-meter which indicates or records the maximum demand ob¬ 
tained through integration. 

(c) Lagged-Demand-Meter: A lagged-demand-meter is a demand- 
meter in which the indication of maximum demand is subject to a 
characteristic time lag. 

8020* Period of an Instrument. The period of an instrument, some¬ 
times called the “periodic time,” is the time taken for the pointer to 
make one complete oscillation (two consecutive swings). A swing is a 
complete movement in either direction. 

8030 Instrument Transformer. An instrument transformer is a trans¬ 
former suitable for use with measuring instruments; that is, one in 
which the conditions of phase and of current or potential in the 
primary circuit, are represented with acceptable accuracy in the 
secondary circuit. An instrument transformer may be either an 
instrument current transformer or an instrument potential (voltage) 
transformer. 

8031* Secondary Burden. The secondary burden of a current trans¬ 
former is an expression in ohms and henrys of the resistance and 
inductance of the external circuit connected to the secondary of that 
transformer. 

8032 Voltage Ratio of Instrument Transformer. The voltage ratio of 
an instrument potential transformer is the ratio of the r.m.s. primary 
terminal voltage to the r.m.s. secondary terminal voltage, under 
specified secondary burden. 

8033 Current Ratio of Instrument Transformer. The current ratio 
of an instrument current transformer is the ratio of r.m.s. primary 
current to r.m.s. secondary current, under specified secondary burden. 

8034 Marked Ratio of Instrument Transformer. The marked ratio 
of an instrument transformer is the ratio which the apparatus is 
designed to give under average conditions of use. When a precise 
ratio is required, it is necessary to specify the voltage or current, 
frequency, load and secondary burden. 

OPERATION. 

8101 Permissible Temperature in Shunts. —(a) General: The limiting 
observable temperature of shunts measured by Method I shall 
not exceed 120°C. 

(b) Exceptions: The above rule shall not apply to shunts 
having no soldered joint and made of material which is not per- 

(8020) In strongly damped instruments, the period is influenced by the amplitude of the 

movement. 

(8031) Considerable uncertainty of meaning has been occasioned by the use of the 

terms, load, secondary load, and secondary connected load for this quantity, and such use 

is discouraged. 



90 


STANDARDS OF THE A. I. E. E. 


manently changed in resistance if continuously subjected to a higher 
temperature. 

8110 Grounding of Meters and Instruments. The covers of meters and 
instruments, which are used with current and potential transformers, 
shall be connected to the grounded sides of the secondary circuits of 
such transformers in all cases where the indications of the instrument 
are liable to be influenced by electrostatic action. 

8111 Instrument Current Transformers on Open Secondary Circuit. 
Under conditions of open secondary circuit, current transformers 
shall be capable of carrying continuously rated primary current 
without damage to the primary insulation and without interruption 
of service. 

8112 Instrument Current Transformers on Closed Secondary Circuit. 

Under conditions of closed secondary circuit, current transformers 
shall withstand 40 times rated current applied for 1 second, without 
injury. 

RATING 

8200 General. The rating of a meter is a designation assigned by 
the manufacturer to indicate its operating limitations. The full scale 
marking of an instrument does not necessarily correspond to its 
rating, but if the rating differs from the full scale marking, the rating 
shall be marked on the instrument. 

8201 Standard Ambient Temperature. —For purposes of rating meters 
and shunts, the standard ambient temperature shall be 40°C. See 

§§8301 and 2211. 

8202 Rating Limitation of the Circuits of Meters and Instruments. No 

circuit of a meter or instrument shall be given a rating higher than 
that corresponding to the maximum current or voltage to which it 
may be continuously subjected. 

8203* Temperature Rise of Meter and Instrument Windings. The 

permissible temperature rises in meters and instruments shall be 
based upon the temperatures specified in §1005 and the standard 
ambient temperature of 40° C. 

8204 Temperature Rise in Shunts. Shunts shall be rated in accordance 
with their observable temperature rise by Method 1, assuming 
the ultimate temperatures specified in §8101 and an ambient tem¬ 
perature specified in §8201. 

TESTS. 

8300 Measurement of Temperature Rise of Shunts. Observable 
temperature shall be measured in such a manner as not to cause 
local change of temperature. 

8301 Standard Temperature of Reference for Meter and Instrument 
Characteristics. The standard temperature of reference for meter 
and instrument characteristics shall be 20° C. See §§8201, 2211. 

(8203) Heating is frequently an immaterial consideration in determining the rating of 

meters and instruments. Losses, impairment of accuracy and other factors often determine 

the rating. 



METERS AND INSTRUMENTS 


91 


8302 Damping. The pointer being at zero before any load is applied, 
damping shall be measured by suddenly applying and maintaining a 
load which will give a steady deflection of one-half full angular scale, 
and observing the following quantities: 

(a) The number of swings taken by the pointer in coming to rest. 

( b) The time, in seconds, required for the pointer to come to rest. 

( c) The overshooting, in per cent of the angular displacement due 
to the disturbance. 

Dielectric Strength of Instrument Transformers. 

8310 Test Voltage Instrument Potential Transformers. The test 
voltage for instrument potential transformers shall be twice the 
normal voltage of the circuit to which it is connected plus 1000 volts. 

8311 Test Voltage of Instrument Current Transformers. The test 
voltage of instrument current transformers shall be 2 }4 times the 
rated voltage plus 2000 volts. 

8312 Test Voltage for Meters and Instruments. (The Institute is 
not at present in a position to make recommendations.) 

SPECIFICATION OF CHARACTERISTICS. 

8600 Errors of Indicating Instruments. In specifying the accuracy of an 
indicating instrument, the error at any point on the scale shall be ex¬ 
pressed as a percentage of the full scale reading. 

8601 Torque. The torque of meters and instruments shall be expressed 
in millimeter-grams. 

8602 Damping. The damping of an instrument shall be expressed in 
terms of the quantities enumerated in §8302, all three of which are 
essential to a complete description. 

8603* Marking of Switchboard Shunts. The marking of switchboard 
shunts shall include the rating in amperes, the drop in volts at that 
rating, and the serial number of any instrument in connection with 
which the shunt may be calibrated. When shunts are designed to be 
used with devices taking sufficient current to be an appreciable pro¬ 
portion of the whole, this fact shall be indicated. 

BIBLIOGRAPHY. 

United States. 

Association of Edison Illuminating Companies and National 
Electric Light Association: Joint Meter Code. 

Bureau of Standards, Circular No. 56, entitled “Standards for 
Electric Service.” 

Foreign 

British Engineering Standards Association: Standard Specifications 
for Indicating Ammeters, Voltmeters and Wattmeters; Standard 
Specifications for Recording (Graphic) Ammeters, Voltmeters, 
and Wattmeters, Standard Specifications for Instrument Trans¬ 
formers; Standard Specifications for Electricity Meters. _ 

(8503) For example, if with 100 amperes rated load in the main circuit, a measuring 

device takes 10 amperes, leaving 100 less 10 amperes in the shunt with a drop of 0.050 

volts, the shunt shall be'marked: Volts 0.050. Amperes 100 less 10. 





92 


STANDARDS OF THE A. I. E. E. 


CHAPTER IX. 

STANDARDS FOR WIRES AND CABLES 

DEFINITIONS. 

9000* Wire.—A wire is a slender rod or filament of drawn metal. 

9001* Conductor. —A conductor is a wire or combination of wires not 
insulated from one another, suitable for carrying a single electric 
current. 

9002* Stranded Conductor. —A stranded conductor is a conductor com¬ 
posed of a group of wires, or of any combination of groups of wires. 

9003 Strand. —A strand is one of the wires, or groups of wires, of any 

stranded conductor. 

9004* Cable. —A cable is either a stranded conductor (single-conductor 
cable), or a combination of conductors insulated from one another 
(multiple-conductor cable). 

9005* Stranded Wire. —A stranded wire is a group of small wires, used 
as a single wire. 

(9000) The definition restricts the term to what would ordinarily be understood by the 
term “solid wire.” In the definition, the word “slender” is used in the sense that the 
length is great in comparison with the diameter. If a wire is covered with insulation, it 
ia properly called an insulated wire; while primarily the term “wire" refers to the metal, 
nevertheless when the context shows that the wire is insulated, the term “wire” will-be 
understood to include the insulation. 

(9001) The term “conductor” is not to include a combination of conductors insulated 
from one another, which would be suitable for carrying several different electric currents. 
Rolled conductors (such as bus-bars) are, of course, conductors, but are not considered 
under the terminology here given. 

(9002) The wires in a stranded conductor are usually twisted or braided together. 
(9004) The first kind of cable is a single conductor, while the second kind is a group of 
several conductors. The component conductors of the second kind of cable may be either solid 
or stranded,and this kind of cable may or may not have a common insulating covering. The 
term “cable” is applied by some manufacturers to a solid wire heavily insulated and lead- 
covered; this usage arises from the manner of the insulation, but such a conductor is not 
included under this definition of “cable.” The term “cable” is a general one, and in prac¬ 
tise, it is usually applied only to the larger sizes. A small cable is called a “stranded wire” 
or a “cord”, both of which are defined below. Cables may be bare or insulated, and the 
latter may be armored with lead, or with steel wires or bands. 

(9005) A wire has been defined as a slender rod or filament of drawn metal. If such a 
filament is subdivided into several smaller filaments or strands, and is used as a single 
wire, it is called a “stranded wire.” There is no sharp dividing line of size between a 
“stranded wire” and a “cable”. If used as a wire, for example in winding inductance coils 
or magnets, it is called a stranded wire and not a cable. If it is substantially insulated, it 
is called a “cord”, defined below. 



WIRES AND CABLES 


93 


9006* Cord.—A cord is a small cable, very flexible and substantially 
insulated to withstand wear. 

9007 Concentric Strand.—A concentric strand is a strand composed of a 
central core surrounded by one or more layers of helically-laid wires 
or groups of wires. 

9008 Concentric-Lay Cable.—A concentric-lay cable is a single-conduc¬ 
tor cable composed of a central core surrounded by one or more layers 
of helically-laid wires. 

9009* Rope-Lay Cable.—A rope-lay cable is a single-conductor cable 
composed of a central core surrounded by one or more layers of heli¬ 
cally-laid groups of wires. 

9010* N-Conductor Cable.—An N-conductor cable is a combination of 
N conductors insulated from one another. 

9011* N-Conductor Concentric Cable.—An N-conductor concentric cable 
is a cable composed of an insulated central conductor with (N-l) 
tubular stranded conductors laid over it concentrically and separated 
by layers of insulation. 

9012* Duplex Cable.—A duplex cable is a cable composed of two insu¬ 
lated stranded conductors twisted together. 

9013 Twin Cable.—A twin cable is a cable composed of two insulated 
stranded conductors laid parallel, having a common covering. 

9014 Twin Wire.—A twin wire is a cable composed of two small insu¬ 
lated conductors laid parallel, having a common covering. 

9016* Triplex Cable.—A triplex cable is a cable composed of three 
insulated single-conductor cables twisted together. 

9016* Twisted Pair.—A twisted pair is a cable composed of two small 
insulated conductors, twisted together, without a common covering. 
9017* Sector Cable.—A sector cable is a multiple-conductor cable in 
which the cross-section of each conductor is substantially a sector, an 
ellipse, or a figure intermediate between them. 

9018 Round Conductor.—A round conductor is either a solid or stranded 
conductor of which the cross-section is substantially circular. 

(9006) There is no sharp dividing line in respect to size between a “cord” and a “cable,” 
and likewise no sharp dividing line in respect to the character of insulation between a 
“cord” and a “stranded wire.” Rubber is used as the insulating material for many classes 
of cords. 

(9009) This kind of cable differs from the preceding in that the main strands are them¬ 
selves stranded. 

(9010) It is not intended that the name as here given be actually used. One would 
instead speak of a “3-conductor cable,” a “12-conductor cable” etc. In referring to the 
general case, one may speak of a “multiple-conductor cable" (as in §9004 above.) 

(9011) This kind of cable usually has only two or three conductors. Such cables are 
used particularly for alternating currents. The remark on the expression “N-conductor" 
given for the preceding definition also applies here. 

(9012) They may or may not have a common insulating covering. 

(9015) They may or may not have a common insulating covering. 

(9016) The two conductors of a “twisted pair” are usually substantially insulated, so 
that the combination is a special case of a “cord.” 

(90171 Sector cables are used in order to obtain decreased overall diameter and thus 
permit the use of larger conductors in a cable of given diameter. 



94 


STANDARDS OF THE A. I . E. E. 


9019* Split Conductor.—A split conductor is a conductor which is 
divided into two or more parts, separated from one another by- 
insulation which is thin compared with the insulation around the 
conductor. 

9030 Factor of Assurance.—The factor o. assurance o? wire or cable 
insulation is the ratio of the voltage at which it is tested to that 
at which it is used. 

9031 Insulation Resistance.—The .insulation resistance of an insulated 
conductor is the electrical resistance offered by its insulation, to an 
impressed voltage tending to produce a leakage of current through 
the same. 

9032* Circular Mil.—A circular mil is a unit of area equal to 
7T 

(=0.7854. . .) of a square mil. The cross-sectional area of a 

circle in circular mils is therefore equal to the square of its diameter 
in mils. A circular inch is equal to a million circular mils. 

9033* Lay.—The lay of any helical element of a cable is the axial 
length of a turn of the helix of that element. 

9034 Direction of Lay.—The direction of lay is the lateral direction in 
which the strands of a cable run over the top of the cable as they 
recede from an observer looking along the axis of the cable. 


ANNEALED COPPER STANDARD 


9060* Standard Annealed Copper.— (a) General: The following shall 

be taken as normal values for standard annealed copper. 


C b ) Resistance: At a temperature of 20° C., the resistance of a 
wire of standard annealed copper one meter in length and of a uni¬ 
form section of liquare millimeter is 1/58 ohm = 0.017241. . . .ohm. 

(c) Density. At a ’temperature of 20°C., the density of standard 
annealed copper is 8.89 grams per cubic centimeter. 


(d) Temperature Coefficient of Resistance: At a temperature 
of 20 C., the constant mass” temperature coefficient of resistance 
of standard anne aled copper, measured between two potential points 

(9019) The term split conductor usually designates a conductor in two parts or splits, 
which may be either concentric or external to one another. 

(9032) A mil is the one-thousandth part of an inch. There are 1974 circular mils in a 
square milimeter. 

(9033) Among the helical elements of a cable may be each strand in a concentric-lay 
cable, or each insulated conductor in a multiple conductor cable. 

(9050) See I. E. C. Publication No. 28, “International Standard of Resistance for Cop¬ 
per”, March, 1914. 

Paragraphs (b) and (e) define what are-sometimes called “Volume Resistivity” and 
“Mass Resistivity”, respectively. This may be expressed in other units as follows: 


Volume Resistivity =1.7241 microhms-cm. (microhms in a centimeter cube) at 
20° C. 

Mass Resistivity = 875.20 ohms (mile, pound) at 20° C. 

For detailed specifications of commercial copper see the Standard Specifications of the 
American Society for Testing Materials. 





WIRES AND CABLES 


95 


rigidly fixed to the wire, is 0.00393 = 1/254.45_per degree centi¬ 

grade. 

(e) Resistance of Standard Annealed Copper at 20° C: As a 
consequence, it follows from (a) and (b) that, at a temperature of 
20 C. the resistance of a wire of standard annealed copper of uni¬ 
form section, one meter in length and weighing one gram, is (l/58) 
X 8.89 = 0.15328.... ohm. 

OPERATION 

Temperature Limits. 

9100* Maximum Temperatures.—The temperature of the insulation of a 
wire or cable at the surface of the conductor shall not be allowed to 
exceed the following values. 

Let t = maximum safe temperature 

E = r. m. s. operating electromotive force in kilovolts between 
conductors 

Impregnated paper, t = 85— E 

Varnished cambric, t = 75— E 

E 

Rubber insulation, t = 60- 

4 

DESIGNATION 

9200 Designation of Wires by Diameter or Gage Number.—The sizes of 
wires shall be stated by their diameters in mils, the American Wire 
Gage (Brown and Sharpe) sizes being taken as standard. For 
brevity, in cases where the most careful specification is not required, 
the sizes of wires may be stated by the gage number in the American 
Wire Gage. 

9201 Designation of Cables by Cross-Sectional Area.—The sizes of 
stranded conductors shall be stated by their cross-sectional area in 
circular mils or circular inches, except in the case of flexible stran¬ 
ded conductors, for which see §9402. The cross-sectional area of a 

(9100) For example: At a working pressure of 3.3 kv., the maximum safe limiting 
temperature at the surface of the conductor, or conductors, in a cable would be as follows: 

For impregnated paper 81.7 °C. 

“ varnished cambric 71.7 °C. 

“ rubber insulation 59.2 °C. 

The life of the insulation of a cable depends in a great measure upon the actual tempera¬ 
ture attained by the insulation. The result of operating at temperatures in excess of the 
safe limit is to shorten the life of the insulating material. When the safe limits are ex¬ 
ceeded, deterioration is rapid and permanent, the damage increasing with the length of 
time that the excessive temperature is maintained and with the amount of excess tempera • 
ture until finally the insulation breaks down. 

Some of the older types of cable for voltages above 7500 have a dielectric loss that is so 
high that it may add considerably to the heating that would otherwise result. In such 
cases the dielectric loss is a material factor in determining the safe load to be carried by the 
cable, and the safe operating temperature will be determined by the temperature at which 
cumulative heating occurs under the conditions of service, if this occurs at a lower tempera¬ 
ture than that at which the insulation deteriorates. 



96 


STANDARDS OF THE A. I. E. E. 


cable shall be considered to be the sum of the cross-sectional areas of 
its component wires, when measured perpendicular to their axes. 
The sizes of stranded conductors smaller than 250,000 circular mils 
( i.e ., No. 0000 A.W.G. or smaller) may be stated by means of the 
gage number of a solid wire having the same cross-sectional area. 

9202* Conductivity.—The conductivity of the metal of wires shall be 
expressed in terms of the conductivity of the Annealed Copper 
Standard, as defined in §9050. 

9203* Copper-Wire Tables.—The copper-wire Tables published by the 
Bureau of Standards in Circular No. 31 are adopted. Table VI 
therein gives the values of diameters and cross-sections of A. W. 
G. sizes to four significant figures. These Tables are based upon 
the Annealed Copper Standard described in §9050. 

TESTS. 

General 

9300 Cable Lengths Tested.—Electrical tests of insulation on wires 
and cables shall be made on the entire lengths to be shipped. 

9301 Immersion in Water.— (a) General: The outer surface of the 
insulation of complete insulated wires and cables shall be grounded 
while being electrically tested. If the insulation is not provided 
with a conducting covering, and if the covering is not liable to injury 
by water, the ground shall be obtained by immersing the insulated 
wire or cable in water for at least twelve hours and testing at the 
end of that period while immersed. If the outer covering is sus¬ 
ceptible to injury by immersion, the insulated conductor shall be 
tested before the application of such covering. 

Dry core paper insulated lead covered cables, such as telephone and 
telegraph cables, for use in water, shall be tested after at least 
twelve hours immersion. 

(b) Multiple-Conductor Cable: In the case of multiple-conductor 
cables, without waterproof overall jacket of insulation, no immersion 
test should be made on finished cables, but only on the individual con¬ 
ductors before assembling. 

Tests of Dielectric Strength 

9310 Object of Tests.—High voltage tests are intended to detect 
weak spots in the insulation and to determine whether its 

(9202) For any given wire, let 

C = conductivity, in per cent of Annealed Copper Standard 
L = length, meters 
R = resistance, ohms 
W = weight, grams 
t = temperature, degrees centigrade 
Then the conductivity may be derived from the following formula: 

15.328 

C “ WR 

— + 0.000597 (20—0 

(9203) For detailed specifications of commercial copper, see the Standard Speci¬ 
fications of the American Society for Testing Materials. 





WIRES AND CABLES 


97 


dielectric strength is sufficient for enabling it to withstand the 
voltage to which it is likely to be subjected in service, with a suitable 
factor of assurance. 

9311 Nature of Tests.—High-voltage tests shall be made at the 
factory, by applying an alternating voltage between the conductor 
and sheath or water. The initially applied voltage must not be 
greater than the working voltage, and the rate of increase shall be 
approximately uniform and not over 100 per cent in 10 seconds. 

9312* Magnitude and Duration of the Test Voltage.—(a) General: 
Wires and cables shall be tested at the place of manufacture for five 
consecutive minutes, except as provided in § 9312 (b) and (f). 

( b) Rubber Insulation , National Electrical Code: Rubber covered 
wires and cables for working pressures up to 600 volts alternating, 
insulated in accordance with the requirements of the National 
Electrical Code, shall be tested in accordance with that Code. 

( c ) 30% to 40% Hevea Rubber Insulation for Pressures up to 600 
Volts, a-c .: Wires and cables for working pressures up to 600 volts 
alternating, insulated with 30% to 40% Hevea rubber compound, 
unless the insulation thickness is less than specified in §9405, shall 
be tested in accordance with Table 901. 


TABLE 901 

High Voltage Tests for Rubber Insulated Wires and Cables. 

(30% to 40% Hevea Rubber Insulation for working pressures up to 600 Volts a-c.) 


Size A. W. G. or 

Size 

Test pressure 

Cir. Mils. 

Sq. mm. 

kilovolts 

14-8 

2.081 - 8.366 

3.0 

7-0000 

10.55 -107.2 

3.5 

250,000 & larger 

127 and larger 

4.0 


(i d ) Thirty to Forty per cent Hevea Rubber Insulation for Pressures 
over 600 Volts A-C: Wires and cables insulated with 30% Hevea 
rubber compound for working pressures over 600 volts alternating, 
shall be tested with one kilovolt per 64th inch of thickness (2.53 kv, 
per mm.) up to 10/64th inch, (3.96 mm.) Above 10/64ths inch, 
(3.96 mm.), the test pressure shall be 10 kilovolts plus 1.5 kilovolts 
per 64th inch (3.79 kv. per mm.) additional up to 30/64ths inch 
(11.89 mm.). Where the insulation thickness is 16/64ths inch 
(6.34 mm.) or over, this rule shall apply only to conductors over 
26,000 cir. mils (13.2 sq. mm.) area. 

(e) Varnished Cambric and Impregnated Paper Insulation: Varn¬ 
ished cambric and impregnated paper insulated wires or cables 
shall be tested in accordance with Table 902. 

(9312-c) Hevea rubber is rubber from the Hevea Brasiliensis tree. Compounds con¬ 
taining 30 to 40% of Hevea rubber have electrical and mechanical properties superior to 
compounds insulated in accordance with the requirements of the National Electric Code. 

(9312-e) Different engineers specify different thickness of insulation for the same work¬ 
ing voltages. Therefore, at the present time the test kv. corresponding to working kv. 
given in Table 902, are based on the minimum thickness of insulation specified by 
engineers and operating companies. 









98 


STANDARDS OF THE A. I. E. E. 


TABLE 902 

High-Voltage Tests for Varnished Cambric or Impregnated Paper Insu¬ 
lated Cables. 

(Minimum Values.) 


Operating kv. 

Test kv. 

Operating kv. 

Test kv. 

Below 0.5 

2.5* 

5 

14 

0.5 

3 

7.5 

19.5 

1 

4 

10 

25 

2 

6.5 

over 10 

2]/2 times oper¬ 

3 

9 


ating pressure 

4 

11.5 




♦The minimum thickness of insulation shall be 1/16 in. (1.6 mm.) 


For intermediate working voltages, the test voltage shall be interpolat *d. 

(/) Telephone, Telegraph and Annunciator Wires and Cables: 
Section 9312 shall not apply to wires and cables for telephone, 
telegraph, annunciator and similar devices. 

9313 Frequency of Test Voltage.—The frequency of the test voltage 
shall not exceed 100 cycles per second, and should approximate as 
closely as possible to a sine wave. The source of energy should be of 
ample capacity. 

9314 Dielectric Strength Tests.—Ultimate dielectric strength tests, when 
required, shall be made on samples not more than 6 meters (20 ft.) 
long. The maximum allowable temperature, at which the test is 
made, for the particular type of insulation and the particular working 
pressure, shall be not greater than the temperature limits given in 
§9100. 

9316 Multiple-Conductor Cables.—If a multiple conductor cable is 
designed for the same operating voltage between conductors and 
sheath or water as between conductors, each conductor shall be 
tested against the other conductors connected together and to the 
sheath or water. If the cable is designed for an operating voltage 
between conductors and ground different from that between con¬ 
ductors, the test between conductors and the sheath or water shall 
be made separately and shall be based on the normal operating 
voltage between conductors and sheath or water as prescribed in 
§9312. 

Insulation Resistance 

9320* Expression of Insulation Resistance.—Insulation resistance 

shall be expressed in megohms. Linear insulation resistance, or the 
insulation resistance of unit length, shall be expressed in terms of the 
megohm-kilometer, or the megohm-mile, or the megohm-thousand- 
feet, and shall be corrected to a temperature of 15.5° C., using a 

(9320) In the case of dry core paper insulated cables, the temperature coefficient of 
insulation resistance cannot be closely determined on account of variations in design and 
manufacture. Therefore no temperature corrections shall be applied to insulation resis¬ 
tance tests. Tests should be made at a temperature of 15.5 ° C. or higher. 













WIRES AND CABLES' 


99 


temperature coefficient determined experimentally for the insulation 
under consideration. 

9321 Megohms Constant.—The megohms constant of an insulated 
conductor shall be the factor “ K ” in the following equation: 

R = K logio —~— 
a 

where R = insulation resistance, in megohms, for a specified unit 
length. 

D = outside diameter of insulation. 
d = diameter of conductor. 

Unless otherwise stated, K will be assumed to correspond to the mile 
unit of length. 

9322 Measurement of Insulation Resistance.—The apparent insula¬ 
tion resistance should be measured after the high-voltage test, 
measuring the leakage current after a one-minute electrification, with 
a continuous e.m.f. of from 100 to 500 volts, the conductor being 
maintained negative to the sheath or water. 

9323 Insulation Resistance of Multiple-Conductor Cables.—The insula¬ 
tion resistance of each conductor of a multiple-conductor cable shall 
be the insulation resistance measured from each conductor to all the 
other conductors in multiple with the sheath or water. 

Capacitance or Electrostatic Capacity 

9330* Expression of Capacitance.—Capacitance shall be expressed in 
microfarads. Linear capacitance, or the capacitance of unit length, 
shall be expressed in microfarads per unit length (kilometer, or mile, 
or one thousand feet), and shall be corrected to a temperature of 
15.5° C., using a temperature coefficient determined experimentally 
for the insulation under consideration. 

9331 Microfarads Constant.—The microfarads constant of an insulated 
conductor shall be the factor “ K" in the following equation: 


Logi 0 — 

where C = capacitance in microfarads per unit length. 

D = outside diameter of insulation. 
d = diameter of conductor. 

Unless otherwise stated, K will be assumed to refer to the mile 
unit of length. 

(9330) In the case of dry core paper insulated cables, the temperature coefficient of 
capacitance cannot be determined closely on account of variations in design and manufac¬ 
ture. Therefore no temperature corrections shall be applied to capacitance tests. Tests 
should be made at a temperature of 15.5° C. or higher. 






100 


STANDARDS OF THE A. I. E. E 


TABLE 903 

Proposed Standard Cables 

(This table is offered for consideration but will not be recommended for final adop¬ 
tion \mtil ratified by other societies interested.) 


Strands 

Total 
nominal 
cross section 
circular 
mils 

Total 

diam. 

inches 

Number & 
Size. See 

Note 4. 

Individual wires 

Nominal diam. 
mils 

Nominal 
cir. mils. 

127 No. 8 

128.5 

16,510 

2,097,000 

1.671 

127 No. 9 

114.4 

13,090 

1,662,000 

1.487 

91 No. 8 

128.5 

16,510 

1,502,000 

1.414 

91 No. 9 

114.4 

13,090 

1,191,000 

1.258 

61 No. 8 

128.5 

16,510 

1,007,000 

1.157 

61-121 mils 

121.0 

14,641 

893,100 

1.089 

61 No. 9 

114.4 

13,090 

798,500 

1.030 

61-107 mils 

107.0 

11,449 

698,400 

.963 

61 No. 10 

101.9 

10,380 

633,200 

.917 

37-116 mils 

116.0 

13,456 

497,900 

.812 

37 No. 10 

101.9 

10,380 

384,100 

.713 

37-97 mils 

97.0 

9,409 

348,100 

.679 

37 No. 11 

90.74 

8,234 

304,700 

.635 

19 No. 9 

114.4 

13,090 

248,700 

.572 

19-107 mils 

107.0 

11,449 

217,500 

.535 

19 No. 11 

90.74 

8,234 

156,400 

.454 

19 No. 12 

80.81 

6,530 

124,100 

.404 

19 No. 13 

71.96 

5,178 

98,380 

.360 

19 No. 14 

64.08 

4,107 

78,030 

.320 

7 No. 10C. 

101.9 

10,380 

72,660 

.306 

7 No. 11 

90.74 

8,234 

57,640 

.272 

7 No. 12 

80.81 

6,530 

45,710 

.242 

7 No. 14 

64.08 

4,107 

28,750 

.192 

7 No. 16 

50.82 

2,583 

18,080 

.152 

7 No. 18 

40.30 

1,624 

11,370 

.121 

7 No. 20 

31.96 

1,022 

7,154 

.096 

7 No. 22 

25.35 

642.4 

4,497 

.076 

7 No. 24 

20.10 

404.0 

2,828 

.060 


Note 1. Nominal diameters and circular mils of the individual wires are taken from 
Table VI, circular No. 31 of the Bureau of Standards. 

Note 2. The variation of the mean diameter of any wires shall not exceed 1 pe r 
cent above or below the nominal diameter. 

Note 3. The variation of the total cross-section of the cable shall not exceed 1 per 
cent above or below the nominal cross-section. 

Note 4. Sizes are expressed as A. W. G. numbers except where diameters are 
given in mils. 


i < 

< C <■ 













WIRES AND CABLES 


101 


9332 Measurement of Capacitance.—The capacitance of cable shall 
be measured with alternating current by comparison with a standard 
condenser. It is preferable that the measurement be made either 
at a frequency approximating that of operation or at a frequency 
giving results approximating those corresponding to the operating 
frequency or frequencies. 

9333 Capacitance of Paired Cables.—The capacitance of paired cables 
shall be measured between the two conductors of any pair, the 
other wires being connected to the sheath or ground. 

9334 Capacitance of Multiple-Conductor Cables (not paired).—The 
capacitance of multiple conductor (not paired) cables shall be 
measured between conductors, and also between each conductor 
and the other conductors connected to the sheath or ground. 

CONSTRUCTION 

Stranding 

9400* Proposed Standard Cables. —Insulated cables not requiring 
special flexibility shall be made of the number and size strands 
specified in Table 903. 

9401 Cables not Requiring Special Flexibility.—Cables not requiring 
special flexibility and not made in accordance with §9400 shall be 
stranded in accordance with Table 904. 


TABLE 904 

Standard Stranding of Concentric-Lay Cables 




Number of Wires (See note 2) 



A 

B 

SIZE 

Sq. mm. 

Bare, insulated or 

Insulated cables 

(See note 1.) 


weatherproof 

for other than 



cables for aerial use. 

aerial use. 

2.0 Cir. Inches 

1013 

91 

127 

1.5 

760 

61 

91 

1.0 

507 

61 

61 

0.6 

304 

37 

61 

0.5 

253 

37 

37 

0.4 

203 

19 

37 

0000 A. W. G. 

107 

19 or 7 (See note 3.) 

19 

00 

67.4 

7 

19 

2 

33.6 

7 

7 

7 and smaller 

10.5 


7 


Note 1. For intermediate sizes, use stranding for next larger size. 

Note 2. Conductors of 0000 A. W. G. and smaller are often made solid and this 
table of stranding should not be interpreted as excluding this practice. 

Note 3. Class A cable, sizes 0000 and 000 A. W. G., is usually made of 7 strand 8 
when bare and 19 strands when insulated or weatherproof. 


(9400) The basis of this rule is the use of strands of American Wire Gage sizes. To 
meet existing operating conditions, four sizes of strands other than American Wire Gage 
sizes have been deemed necessary and their diameters are shown in mils. 









102 


STANDARDS OF THE A. I. E. E. 


9402* Flexible Cables. —Conductors of special flexibility should ordi¬ 
narily be made with wires of regular A.W.G. sizes, and rated by the 
number and size of wires. The stranding of flexible cables is given 
in Table 905. 


TABLE 905 

Stranding of Flexible Cables 


Nearest 

A.W.G. 

size 

(see Note 1) 

Circular 

mils 

(see Note 2) 

Diam. 

of 

•cable, 

mils 

No. of 
wires 

Size of each wire 

Construction 
(see Note 3) 

1 

A.W.G. 

Diam. 

mils 


2039000 

1885. 

703 

15.5 

53.9 

37 X 19 


1816000 

1779. 

ii 

16.0 

50.8 

ii 


1617000 

1679. 

a 

16.5 

48.0 

ii 


1440000 

1584. 

a 

17.0 

45.3 

a 


1284000 

1496. 

a 

17.5 

42.7 

a 


1103000 

1372. 

427 

16.0 

50.8 

61 X 7 


874600 

1222. 

ii 

17.0 

45.3 

ii 


693600 

1088. 

ii 

18.0 

40.3 

a 


550000 

969. 

it 

19.0 

35.9 

a 


436200 

863. 

ii 

20.0 

32.0 

a 


345900 

768. 

U 

21.0 

28.5 

a 


274300 

684. 

a 

22.0 

25.3 

ii 

* 


264600 

671. 

259 

20.0 

32.0 

37 X 7 

0000 

209800 

598. 

it 

21.0 

28.5 

ii 

000 

171300 

538. 

133 

19.0 

35.9 

19 X 7 

00 

135900 

479. 

ii 

20.0 

32.0 

ii 

0 

107700 

427. 

ii 

21.0 

28.5 

ii 

1 

82780 

332. 

91 

20.5 

30.2 

Concentric 

2 

65650 

295. 

ii 

21.5 

26.9 

ii 

3 

52060 

263. 

ii 

22.5 

23.9 

ii 

4 

39190 

228. 

61 

22.0 

25.3 

ii 

5 

31080 

203. 

ii 

23.0 

22.6 

a 

6 

24650 

181. 

ii 

24.0 

20.1 

a 

8 

17410 

152. 

ii 

25.5 

16.9 

it 

10 

10560 

118. 

37 

25.5 

16.9 

“ 

12 

6640 

94. 

ii 

27.5 

13.4 

a 

14 

4176 

74. 

ii 

29.5 

10.6 

a 




To equal 




Smaller 

.... 

.... 

Required 

30.0 

.... 

Bunched 




Size 





Note 1. The A.W.G. cross-sectional areas except for 61 strands, are approximated 
within 2 per cent. In the case of 61 strand cables the approximation is 6 per cent. 

Note 2. Circular mils are based on theoretical diameters of A.W.G. sizes, which 
vary above or below values given in table by less than 0.1 mil. 

Note 3. “61 X 7” in the rating of a rope-lay cable signifies 61 strands of 7 wire* 
each. 

(9402) Where necessary to closely approximate a regular size cable, the strands may be 
made of half-size wires from No. 15 to No. 30 A. W. G. 


















WIRES AND CABLES 


103 


9403* Correction for Lay.—Two per cent shall be taken as the standard 
increment of resistance and of mass, due to stranding. In cases 
where the lay is definitely known, the increment should be cal¬ 
culated and not assumed. 

Thickness of Insulation 

9405 Thickness of Insulation for Rubber Insulated Wires and Cables.— 

Unless special conditions warrant departures from this rule, the 
thickness of insulation for rubber compounds containing from 30 to 
40 per cent of Hevea rubber, shall be in accordance with Table 906. 


TABLE 906 
Thickness of Insulation 


30 to 40 per cent Hevea Rubber Compound 

Recommended Walls of Insulation, 64ths. Inch. 


Size 

A. W. G. 

or 

Cir. Mils 


Working pressure, volts alternating 

Sq. 

mm. 

600 

or 

less 

1500 

2500 

3500 

5000 

6000 

7000 

8000 

9000 

10000 

11000 

14-8 

2.08-8.37 

3 

6 

8 

10 

12 

14 

16 

18 

20 

22 

24 

7-2 

10.6-33.6 

4 

7 

9 

10 

12 

14 

16 

18 

20 

22 

24 

1-0000 

42.4-107 

5 

8 

10 

10 

12 

14 

16 

18 

20 

22 

24 

250,000- 

500,000 

127-253 

6 

9 

10 

11 

12 

14 

16 

18 

20 

22 

24 

550,000- 

1,000,000 

279-507 

7 

10 

10 

12 

12 

14 

16 

18 

20 

22 

24 

1,250,000- 

2,000,000 

633-1013 

8 

10 

10 

12 

14 

16 

18 

18 

20 

22 

24 


Notes. In multiple conductor cables, the thickness of insulation on each conductor 
shall be based on the highest r. m. s. voltage between the conductor and the outside of 
this insulation. The above table is based upon alternating voltages of commercial 
frequencies. For voltages over 600, the insulation thickness for direct-current cable 
has not been established. For intermediate sizes the insulation thickness should be 
the same as for the next larger sizes. 

BIBLIOGRAPHY 

United States 

American Electric Railway (Engineering) Association: Wire and^Cable 
Specifications. 

Association of Railway Electrical Engineers: Wire and Cable Specifica¬ 
tions. 

(9403) The resistance and mass of a stranded conductor are greater than in a solid 
conductor of the same cross sectional area, depending on the lay (*.*., the pitch of 
the twist of the wires). 


















104 


STANDARDS OF THE A. I. E. E. 


American Society for Testing Materials: Standard Specifications for 
Soft Annealed, Semi-hard and Hard Drawn Copper. 

Joint Rubber Insulation Committee: Specifications and Chemical 
Analysis for Rubber Insulation. (J. Wiley & Sons) 

National Electric Light Association: Wire and Cable Specifications. 

National Fire Protection Association: The National Electrical Code. 

Railway Signal Engineers Association: Wire and Cable Specifications. 

U. S. Bureau of Standards: Copper Wire Tables (Circular No. 31), and 
Wire and Cable Terminology (Circular No. 37). 

Foreign 

British Engineering Standards Association: Standard Specifications for 
Copper Conductors; Report on Hard-Drawn Copper and Bronze Wire. 

Verband Deutscher Electrotechniker: Normalien fur isolierte 

Leitungen in Starktromanlagen. 

International 

International Electrotechnical Commission: International Standard of 
Resistance for Copper. (Publication No. 28.) 



WIRES AND CABLES 


105 


CHAPTER X. 

STANDARDS FOR STORAGE BATTERIES 


Rules to be included in the Chapter have been prepared, and await 
final consideration before publication. 


106 


STANDARDS OF THE A. I. E. E. 


CHAPTER XI. 

STANDARDS FOR ILLUMINATION 

This chapter consists of extracts from the Report of the Committee 
on Nomenclature and Standards of the Illuminating Engineering Society 
for the year 1918. It is here included by permission. 


General 

11000 Radiant flux, 0, is the rate of flow of radiation evaluated with 
reference to energy, and is expressed in ergs per second or in watts. 

11001 Luminous flux, F, is the rate of flow of radiation evaluated with 
reference to visual sensation, and is expressed in lumens. 

11002 Visibility, K\ , of radiation of a particular wave-length is the ratio 
of the luminous flux at that wave-length to the corresponding radiant 
flux. 

Defining equation: 


11003* The Mechanical equivalent of light is the ratio of radiant flux 
to luminous flux for the wave-length of maximum visibility, and is 
expressed in ergs per second per lumen, or in watts per lumen. It is 
the reciprocal of the maximum visibility. 

11004 Luminosity of a particular wave-length is the product of the 
visibility of that wave-length and the corresponding ordinate of the 
spectral curve of radiant flux, and is represented by the ordinate of 
the spectral curve of luminous flux. This curve is called the 
spectral luminosity curve and is different with different sources. 

11005 The Luminous efficiency of any source is the ratio of the 
luminous flux to the radiant flux from the source and is expressed in 
lumens per watt. 

11006 Luminous intensity I, of a source of light in a given direction 
is the solid angular density of the luminous flux emitted by the source 
in the direction considered, when the flux involved acts as far as 
computation and measurements are concerned, as if it came from a 


(11003). This term has been used in a variety of senses. As here defined it refers only to 
the minimum mechanical equivalent of light. The reciprocal of this quantity is some¬ 
times called the luminous equivalent of radiation. 



ILL UMINA TION 


107 


point. Or, it is the flux per unit solid angle from that source in the 
direction considered. The flux from any source of dimensions which 
are negligibly small by comparison with the distance at which it 
is observed, may be treated as if it were emitted from a point. 

Defining equation: 


/ = 


d F 
d CO 


or, if the intensity is uniform, 



CO 

where CO is the solid angle. 


11007 Illumination, E, of a surface at any point is the luminous flux 
density on the surface at that point, or the flux per unit of in¬ 
tercepting area. 

Defining equation: 


or, when uniform, 



where S is the area of the intercepting surface. 

11008* Candle is the unit of luminous intensity maintained by the 
national laboratories of France, Great Britain and the United States. 

11009 Candlepower, cp., is luminous intensity expressed in candles. 

11010* Lumen,/., is the unit of luminous flux equal to the flux emitted 
in a unit solid angle (steradian) by a point source of unit candle- 
power. 


11011 Lux is a unit of illumination equal to one lumen per square 
meter. Using the centimeter as the unit of length, the unit of ill¬ 
umination' is one lumen per square . centimeter, for which Blondel 
has proposed the name phot. One millilumen per square centimeter 
(milliphot) is more useful as a practical unit. One foot-candle is one 
lumen per square foot, and is equal to 1.0764 milliphots. The milli¬ 
phot is recommended for scientific records. 

11012 Brightness of an element of a luminous surface may be expressed 
in either of two ways: (a) in terms of intensity, I, ( b ) in terms of 
flux, F. 

(a) Brightness in terms of the luminous intensity I (or candle- 
power) per unit of projected area of the surface (candlepower bright¬ 
ness) corresponds to the 


(11008). This unit, which is used also by many other countries, has frequently been re¬ 
ferred to as the international candle. 

(11010) A uniform source of one candlepower emits 4 t lumens. 









108 


STANDARDS OF THE A. I. E. E. 


d I 

defining equation, bi — cog q 

where 6 is the angle between the normal to the surface and the line 
of sight. 

(&) Brightness in terms of the flux, F, proceeding from a unit area 
of the surface, on the assumption that the surface is a perfect diffuser; 
i. e. } that it obeys the cosine law of emission or reflection, (lumen 
brightness) corresponds to the 

d F 

defining equation, b F — 

(perfect diffusion assumed). 

The units in which brightness is measured according to (a) and 
(b) differ only in numerical value. 

11013 Lambert, L, is the unit of brightness in the lumen system. 
The lambert is the brightness of a perfectly diffusing surface 
emitting or reflecting one lumen per square centimeter. For 
most purposes the millilambert, 0.001 lambert, is the preferable 
practical unit. 

To say that the brightness of a surface as viewed from a given 
point is n lamberts, signifies that its brightness is the same as that of 
a perfectly diffusing surface emitting or reflecting n lumens per 
square centimeter. 

In practice no surface obeys exactly the cosine law of emission or 
reflection; hence the brightness of a surface generally is not uniform 
but varies somewhat with the angle at which it is viewed. 

A perfectly diffusing surface emitting one lumen per square foot 
will have a brightness of 1.076 millilamberts. 

Brightness expressed in candles per square centimeter may be 
reduced to lamberts by multiplying by 7T = 3.14. 

Brightness expressed in candles per square inch may be reduced to 
lamberts by multiplying by 7r/6.45 = 0.487. 

Surfaces and Media Modifying Luminous Flux 

11020 Diffusing surfaces and media are those which break up the in¬ 
cident flux and distribute it more or less in accordance with the 
cosine law, as for example, white plaster and opal glass. 

11021 Redirecting surfaces and media are those which change the direc¬ 
tion of the luminous flux in a definite manner; as for example, a 
mirror or a lens. 

11022 Scattering surfaces and media are those which redirect the 
luminous flux and break it up into a multiplicity of separate pencisl; 
as for example, ripple glass, reflecting or transmitting. 

11023* Reflection factor, of a body p, is the ratio of the flux reflected by 
the body to the flux incident upon it. The reflection from a 

(11023) (11024) (11025) These terms are introduced to replace the more commonly used 
terms, Coefficient of reflection, Coefficient of absorption, Coefficient of transmission, which 
latter terms refer to the specific properties of materials rather than to the behavior of 
bodies under specified conditions, such as angle of incidence, etc. 





ILLUMINA TION 


109 


body may be regular, diffuse or mixed. In regular reflection 
the flux is reflected at an angle of reflection equal to the angle 
of incidence. In diffuse reflection the flux is reflected in all 
directions. In perfectly diffuse reflection, the distribution of the 
reflected flux is in accordance with Lambert’s cosine law. In most 
practical cases, there is a superposition of regular and diffuse reflec¬ 
tion. 

11024* Absorption factor, of a body a, is the ratio of the flux absorbed 
by the body to the flux incident upon it. 

11025* Transmission factor, of a body r, is the ratio of the flux trans¬ 
mitted by the body to the flux incident upon it. 

p + a + T = 1 

Illumination 

11030 Unidirectional illumination on a surface is that produced by a 
single light source of relatively small dimensions. It is character¬ 
ized by the fact that a small opaque object placed near the ill¬ 
uminated surface casts a sharp shadow. 

11031 Multidirectional illumination on a surface is that produced by 
several separated light sources of relatively small area. It is 
characterized by the fact that a small opaque object placed near 
the illuminated surface casts several shadows. 

11032 Diffused illumination is that produced either by primary or 
secondary light sources having dimensions relatively large with 
respect to the distance from the point illuminated, and scattering 
light in all directions. It is characterized by relative lack of 
shadow. Diffused illumination may be derived principally 
from a single direction as in the light from a skylit window or from all 
directions as in the open air. Perfectly diffused illumination on a 
surface is shadowless. 

In any practical case of illumination on a surface there is usually 
a mixture of the above types. 

11033 Coefficient of utilization of an illumination installation on a 
given plane is the total flux received by that plane divided by the 
total flux from the lamps illuminating it. When not otherwise spec¬ 
ified, the plane of reference is assumed to be a horizontal plane 30 in¬ 
ches (76 cm.) from the floor. 

11034 Variation factor of an illumination installation is the ratio of 
either the maximum or minimum illumination on a given plane to 
the average illumination on that plane. 

11035 Variation range of illumination on a given plane is the ratio of 
the maximum illumination to the minimum illumination on that 
plane. 

11036 Hemispherical ratio for a given lighting unit is the ratio of the 
luminous flux in the upper hemisphere to that in the lower hemi¬ 
sphere. 


no 


STANDARDS OF THE A. I. E. E 


11037 Brightness ratio is the ratio of the brightness of any two surfaces. 
When the two surfaces are opposed, the brightness ratio is commonly 
called the “brightness contrast.” 

Illuminants 

11040 The output of all illuminants should be expressed in lumens. 

11041 Illuminants should be rated upon a lumen basis rather than a 
candlepower basis. 

11042 Lamp efficiency is the ratio of the luminous flux output to the 
power input. 

11043 The lamp efficiency or specific output of electric lamps should 

be stated in terms of lumens per watt and that of illuminants depend¬ 
ing upon combustion should be stated in lumens per British thermal 
unit per hour. 

11044 The power consumption of auxiliary devices which are necess¬ 
arily employed in circuit with a lamp should be included in the input 
of the lamp. For example, the watts lost in the ballast resistance 
of an arc lamp are properly chargeable to the lamp. 

11045 The specific consumption of an electric lamp is its watt con¬ 
sumption per lumen. “Watts per candle” is a term used commerc¬ 
ially in connection with electric, incandescent lamps, and denotes 
watts per mean horizontal candle. 

11046 Life Tests.—Electric incandescent lamps of a given type 
may be assumed to operate under comparable conditions only 
when their lumens per watt consumed are the same. Life test 
results, in order to be compared, must be either conducted under, or 
reduced to, comparable conditions of operation. 

11047 In comparing different luminous sources not only should their 
candlepower be compared, but also their relative form, brightness, 
distribution of illumination and character of light. 

Lamp Accessories 

11048 A reflector is an appliance the chief use of which is to redirect 
the luminous flux of a lamp in a desired direction or directions. 

11049 A shade is an appliance the chief use of which is to di¬ 

minish or to interrupt the flux of a lamp in certain directions where 
such flux is not desirable. The function of a shade is commonly 
combined with that of a reflector. 

11050 A globe is an enclosing appliance of clear or diffusing 

material the chief use of which is either to protect the lamp or to 
diffuse its light. 

Photometry 

11060 Performance curve is a curve representing the behavior of a lamp 
in any particular (candlepower, consumption, etc.) at different 
periods during its life. 

11061 Characteristic curve is a curve expressing a relation between two 
variable properties of a luminous source, as candlepower and volts, 
candlepower and rate of fuel consumption, etc. 


ILLTJMINA TION 


111 


11062 Mean horizontal candlepower of a lamp is the average candle 
power in the horizontal plane passing through the luminous center 
of the lamp. 

It is here assumed that the lamp (or other light source) is mounted 
in the usual manner, or, as in the case of an incandescent lamp, with 
its axis of symmetry vertical. 

11063 Mean spherical candlepower of a lamp is the average candle- 
power of a lamp in all directions in space. It is equal to the total 
luminous flux of the lamp in lumens divided by 4 7T. 

11064 Mean hemispherical candlepower of a lamp (upper or lower) 
is the average candlepower of a lamp in the hemisphere considered. 
It is equal to the total luminous flux emitted by the lamp in that 
hemisphere divided by 2 7T. 

11066 Mean zonal candlepower of a lamp is the average candlepower 
of a lamp over the given zone. It is equal to the total luminous 
flux emitted by the lamp in that zone divided by the solid angle 
of the zone. 

11066* Spherical reduction factor of a lamp is the ratio of the mean 
spherical to the mean horizontal candlepower of the lamp. 

TABLE 1100 

11067 Photometric Units and Abbreviations. 


Photometric 

quantity Name of unit 


Symbols and 
defining 
equations 


Abbrev¬ 
iation 
for name 
of unit 


1. Luminous flux 

2. Luminous 

intensity 

3. Illumination 


4. Exposure 


5. Brightness 


6. Reflection factor 


Lumen 

F . 

1. 

Candle j 

= dF r = 
d CO ’ 

d \p 

'■ „ cp. 

d CO 

Phot, foot- . 
candle, lux E 

d F _ 1 

cos 6. ph. fc. 

~ ~dS ~ r 2 

Phot-second 

Micro phot- 

E t 

phs. fJL phs. 

second 



Apparent candle 



per sq. cm. 
Apparent candle 
per sq. in. 

d I 


dS cos 6 

Lambert 

d F 
hl = dS 

L. mL. 


P 

— 

r — 

a 

— 


(11066). In the case of a uniform point-source, this factor would be unity, and for a 
straight cylindrical filament obeying the cosine law it would beir/4. 

* Perfect diffusion assumed. 












112 


STANDARDS OF THE A. I. E. E. 


8. Transmission factor T 

9. Mean spherical candlepower scp. 

10. Mean lower hemispherical candlepower lcp. 

11. Mean upper hemispherical candlepower ucp. 

12. Mean zonal candlepower ZC P- 

13. Mean horizontal candlepower mhc. 


14. 1 lumen is emitted by 0.07958 spherical candlepower. 

15. 1 spherical candlepower emits 12.57 lumens. 

16. 1 lux = 1 lumen incident per square meter = 0.0001 phot = 0.1 

milliphot. 

17. 1 phot = 1 lumen incident per square centimeter = 10,000 

lux = 1,000 milliphots = 1,000,000 microphots. 

18. 1 m ill iphot = 0.001 phot = 0.929 foot-candle. 

19. 1 foot-candle = 1 lumen incident per square foot = 1.076 

milliphots = 10.76 lux. 

20. 1 lambert = 1 lumen emitted per square centimeter of a perfectly 

diffusing surface. 

21. 1 millilambert = 0.001 lambert. 

22. *1 lumen, emitted, per square foot = 1.076 millilamberts. 

23. *1 millilambert = 0.929 lumen, emitted, per square foot. 

24. 1 lambert = 0.3183 candle per square centimeter = 2.054 

candles per square inch. 

25. 1 candle per square centimeter = 3.1416 lamberts. 

26. 1 candle per square inch = 0.487 lambert = 487 millilamberts. 




TELEPHONY AND TELEGRAPHY 


113 


CHAPTER XII. 

STANDARDS FOR TELEPHONY AND TELEGRAPHY 

Many of the following definitions are tentative and not yet fully 
established. Criticisms and suggestions, addressed to the Secretary 
of the Standards Committee, will be welcomed. Some of the defini¬ 
tions are specific to telephony, and differ in detail from similar 
definitions appearing in other parts of the rules. 

DEFINITIONS 
Line Circuits 

12000 Ground-Return Circuit.—A ground-return circuit is a circuit 
consisting of one or more metallic conductors in parallel, with the 
circuit completed through the earth. 

12001 Metallic Circuit.—A metallic circuit is a circuit of which the 
earth forms no part. 

12002 Two-Wire Circuit.—A two-wire circuit is a metallic circuit 
formed by two parallel conductors insulated from each other. 

12003 Superposed Circuit.—A superposed circuit is an additional cir¬ 
cuit obtained from a circuit normally required for another service, 
and in such a manner that the two services can be given simultane¬ 
ously without mutual interference. 

12004 Phantom Circuit.—A phantom circuit is a superposed circuit, 
each side of which consists of the two conductors of a two-wire 
circuit in parallel. 

12005 Side Circuit.—A side circuit is a two-wire circuit forming one 
side of a phantom circuit. 

12006 Non-Phantomed Circuit.—A non-phantomed circuit is a two- 
wire circuit, which is not arranged for use as the side of a phan¬ 
tom circuit. 

12007 Simplexed Circuit.—A simplexed circuit is a two-wire telephone 
circuit, arranged for the superposition of a single ground-return sig¬ 
nalling circuit operating over the wires in parallel. 

12008 Composited Circuit.—A qomposited circuit is a two-wire tele¬ 
phone circuit, arranged for the superposition on each of its component 
metallic conductors, of a single independent ground-return signalling 
circuit. 

12009 Quadded or Phantomed Cable.—A quadded or phantomed cable 
is a cable adapted for the use of phantom circuits. 

12010 Simplex Circuit.—A simplex circuit in telegraphy is one arranged 
for operation in one direction dt one time. 

12011 Duplex Circuit.—A duplex circuit in telegraphy is one arranged 
for simultaneous operation in opposite directions. 



114 STANDARDS OF THE A. I. E. E. 

12012 Diplex Circuit.—A diplex circuit in telegraphy is one arranged 
for the simultaneous transmission of two messages in the same 
direction. 

12013 Quadruplex Circuit.—A quadruplex circuit in telegraphy is one 
arranged for the simultaneous transmission of two messages in each 
direction. 

12014 Multiplex Circuit.—A multiplex circuit in telegraphy is one 
arranged for the simultaneous transmission of one or more messages 
in both directions. Both duplex and quadruplex are examples of 
multiplex whereas diplex is not. 

12015 Linear Electrical Constants.—The linear electrical constants of 
a line are the electrical constants per unit length of the line, e. g. 
linear resistance, linear inductance, etc. 

12016 Smooth Line.—A smooth line is a line whose electric elements 
are all continuously and uniformly distributed throughout its length. 

12017* Periodic Line.—A periodic line is a line consisting of successive 
similar sections in each of which one or more electric elements are 
not distributed uniformly. As examples of periodic lines are (1) 
loaded lines and (2) artificial lines consisting of successive similar 
sections of lumped constants. 

12018 Equivalent Smooth Line.—An equivalent smooth line of a 
periodic line is a smooth line having the same electrical behavior as 
the periodic line, at a given single frequency, when measured at 
terminals or at corresponding section junctions. 

12019 Equivalent Periodic Line.—An equivalent periodic line of a 
smooth line is a periodic line having the same electrical behavior, for 
an assumed single frequency, as the smooth line, when measured at 
terminals or at corresponding section junctions. The terms conju¬ 
gate smooth line and conjugate periodic line are also sometimes used. 

12020 Composite Line.—A composite line is a line consisting of a 
plurality of successive, sections having different linear electrical con¬ 
stants, as in the case where an underground cable section is joined to 
an overhead open-wire section. 

12021 Loaded Line.—A loaded line is one in which the normal re¬ 
actance of the circuit has been altered for the purpose of increasing 
its transmission efficiency. 

12022 Series Loaded Line.—A series loaded line is one in which the 
normal reactance has been altered by reactance serially applied. 

12023 Shunt Loaded Line.—A shunt loaded line is one in which the 
normal reactance of the circuit has been altered by reactance applied 
in shunt across the circuit. 

(12017) The term periodic in this definition refers to the line constants and not to time 

relations. 



TELEPHONY AND TELEGRAPHY 


115 


12024 Continuous Loading. —-A continuous loading is a series loading 
in which the added inductance is uniformly distributed along the 
conductors. 

12025* Coil Loading. —A coil loading is one in which the normal induc¬ 
tance is altered by the insertion of lumped inductance in the circuit 
at intervals. 

Circuit Constants and Characteristics 

12050 Damping of a Circuit. —The damping at a given point in a circuit 
from which the source of energy has been withdrawn, is the pro¬ 
gressive diminution in the effective value of electromotive force 
and current at that point resulting from the withdrawal of elec¬ 
trical energy. 

12051* Damping Constant.— The damping constant of a circuit is a 
measure of the ratio of the dissipative to the reactive component of 
its admittance or impedance. 

12052* Mutual Impedance. —-The mutual impedance for single fre¬ 
quency alternating currents, between a pair of terminals and a 
second pair of terminals of a network, under any given condition, is 
the negative ratio of the electromotive force produced between either 
pair of terminals on open circuit to the current flowing between the 
other pair of terminals. 

12053* Self-Impedance. —The self-impedance between a pair of ter¬ 
minals of a network, under any given condition, is the ratio of the 
electromotive force applied across the terminals to the entering 
current. 

12054* Characteristic Impedance. —The characteristic impedance of a 
line is the ratio of the applied electromotive force to the resulting 
steady-state current upon a line of infinite length and uniform struc¬ 
ture, or of periodic recurrent structure. 

(12025) This lumped inductance may be applied either in series or in shunt. 

As commonly understood, coil loading is a series loading, in which the lumped inductance 
is applied at uniformly spaced recurring intervals. 

(12051) Applied to the admittance of a condenser or other simple circuit having capacity 
reactance, the damping constant for a harmonic electromotive force of given frequency is 
the ratio of the conductance G, of the condenser or simple circuit at that frequency to twice 
the capacitance, C, of the condenser at the same frequency, (G/2 C). 

Applied to the reactance of a coil or other simple circuit having inductive reactance, the 
damping constant for a harmonic current of a given frequency is the ratio of the resistance, 
R, of the coil or circuit at that frequency to twice the inductance, L, at the same frequency 
(R/2 L). 

(12052) A receiving-end impedance is an example of a mutual impedance. 

Single frequency voltages and currents are here supposed to be represented by complex 
numbers. Their ratio is therefore a complex number. 

(12053) Single frequency voltages and currents are here supposed to be represented 
by complex numbers. Their ratio is therefore a complex number. 

(12054) In practise, the terms (1) line impedance, (2) surge impedance, (3) iterative 
impedance, (4) sending-end impedance, (5) initial sending-end impedance, (6) final sending- 
end impedance, (7) natural impedance and (8) free impedance, have apparently been more 
or less indefinitely and indiscriminately used as synonyms with what is here defined as 
“characteristic impedance.” 

Single frequency voltages and currents are here supposed to be represented by complex 
numbers. Their ratio is therefore a complex number. 



116 


STANDARDS OF THE A. I. E. E. 


12055* Sending-En,d Impedance.—The sending^end impedance of a line 
is the ratio of the applied electromotive force to the resulting steady- 
state current at the point where the electromotive force Is applied. 

12056* Propagation Constant.—The propagation constant of a uniform 
line, or section of a line of periodic recurrent structure, is the natural 
logarithm of the ratio of the steady-state currents at various points 
separated by unit length in a uniform line of infinite length, or at 
successive corresponding points in a line of recurrent structure of 
infinite length. The ratio is determined by dividing the value of the 
current at the point nearer the transmitting end by the value of the 
current at the point more remote.. 

12057 Attenuation Constant.—The attenuation constant for a single 
frequency is the real part of the propagation constant taken at that 
frequency. 

12058 Wave-Length Constant.—The wave-length constant is the 
imaginary part of the propagation constant. 

12059 Standard Cable.—A standard cable is an ideal uniform line in 
terms of which the attenuation of a line or network may be specified. 
It is characterized by the following constants: Linear resistance, 88 
ohms per loop mile (54.7 ohms per loop km.)., Linear capacitance 
between wires 0.054 microfarad per loop mile (0.03355 microfarad 
per loop km.). Linear inductance and linear leakance, 0. 

Equivalent Circuits 

12102* Equivalent Circuit.—An equivalent circuit is a simple network of 
series and shunt impedances, which, at a given frequency, is the 
approximate electrical equivalent of a complex network. 

12103* “Th Equivalent Circuit.—A “T” equivalent circuit is a triple-star 
or ' 1 Y” connection of three impedances externally equivalent to a 
complex network. See Fig. 12-1 for symbol. 

'<*tt j \/W\AA 


Fig. 12-1 

12104* Equivalent Circuit.—An “I” equivalent circuit is a connec¬ 

tion of five impedances in the form shown in Fig. 12-2, which is- ex¬ 
ternally equivalent to a complex network. It differs from the “ T” 
equivalent circuit in that the impedances are arranged symmetrically 

(12055) See note under “Characteristic Impedance,” In case the line is of infinite 
length of uniform structure or of periodic recurrent structure, the sending-end impedance 
and the characteristic impedance are the same. 

Single frequency voltages and currents are here supposed to be represented by complex 
numbers. Their ratio is therefore a complex number. 

(12056) Single frequency voltages and currents are here supposed to be represented 
by complex numbers. Their ratio is therefore a complex number. 

(12102 to 12106 Inch) As ordinarily considered, the simple networks as defined, are the 
electrical equivalents of complex networks only with respect to definite pairs of terminals. 


-AMAAA— 





TELEPHONY AND TELEGRAPHY 


117 


on the two sides of the circuit, which is often desirable in connec¬ 
tion with practical problems, as indicating that the circuit is bal¬ 
anced with respect to ground. 


•—AMA/V 


•—\A/WW 


VWVNA-» 


•vAAAAA.-• 


Fig. 12-2 

12105* “11” Equivalent Circuit. —A “II” equivalent circuit is a delta 

connection of three impedances externally equivalent to a complex 
network. It is also called a “ Z7” equivalent circuit. See Fig. 12-3 
for symbol. 



12106* “ 0 " Equivalent Circuit. —An “0” equivalent circuit is a con¬ 

nection of four impedances in the form shown in Fig. 12-4, externally 
equivalent to a complex network. It differs from the II equivalent 
circuit in that the impedances are arranged symmetrically on the 
two sides of the circuit, which is often desirable in connection with 
practical problems, as indicating that the circuit is balanced with 
respect to ground. 



Telephony 

12200 Manual Telephone System. —A manual telephone system is one 
in which the calling party gives his order to an operator who com¬ 
pletes the call directly by hand, either with or without the assist¬ 
ance of one or m ore additional operators. 

12201 Automatic or Full Mechanical Telephone System. —An automatic 
or full mechanical telephone system is one in which the calling party 
is enabled to complete a call by remote-control switches without the 
aid of an operator. 






118 


STANDARDS OF THE A. I. E. E. 


12202 Semi-Automatic or Semi-Mechanical Telephone System. — A 

semi-automatic or semi-mechanical telephone system is one in which 
the calling party gives his order to an operator who completes the 
call through remote-control switches. 

12203 Telephone Exchange. —A telephone exchange consists of one or 
more central offices with associated plant, by means of which tele¬ 
phone service is rendered in a specified local community. 

12204 Telephone Exchange Area or District. —A telephone exchange 
area or district is the area or district served by a telephone exchange. 

12205 Central Office. —A central office is a switching center for inter¬ 
connecting lines terminating therein. 

12206 Toll Central Office. —A toll central office is one in which toll and 
long distance lines terminate. 

12207 Local Central Office. —A local central office is one in which sub¬ 
scriber’s lines terminate. 

12208 Private Branch Exchange (Generally Abbreviated “P. B. X.”).— 

A private branch exchange is a telephone system generally installed 
on the premises of a subscriber, including a switchboard and ex¬ 
tension sets, and connected to a central office, affording intercom¬ 
munication between the extension sets and also between these sets and 
the central office. 

12209 Private Exchange. —A private exchange is one which serves one 
business organization or individual, and is not connected to a central 
office. 

12210 Private Automatic Exchange. —A private automatic exchange is 
an automatic exchange which serves one business organization or 
individual, and is not connected to a central office. 

12211 Subscriber Set (Often Abbreviated to “Subset”). —A subscriber 
set is an assembly of apparatus for sending and receiving telephone 
calls. 

12212 Subscriber Station (Often Abbreviated to “Substation”).— A 

subscriber station is an installed subscriber set connected to a cen¬ 
tral office for the purpose of sending and receiving telephone calls. 

12213 Pay Station. —A pay -station is a subscriber station available for 
the use of the public on the payment of a fee. The fee may be either 
deposited in a coin box or paid to an attendant. 

12214 Toll Station. —A toll station is a pay station located outside of a 
local service area and affording toll and long distance service only. 

12215 Subscriber line or Subscriber Loop. —A subscriber line or sub¬ 
scriber loop is the wire connection between a subscriber station and the 
central office. 

12216 Subscriber Line Circuit. —A subscriber line circuit is a subscriber 
line with its associated individual central office apparatus. 

12217 Individual Line. —An individual line is a subscriber line which 
connects one subscriber station to a central office, though it may have 
one or more extension sets. 


119 


TELEPHONY AND TELEGRAPHY 

12218 Party Line.— -A party line is a subscriber line which connects two 
or more subscriber stations to a central office. 

12219 Tip Side or Tip Wire, Ring side or Ring Wire. —-The tip side or 
wire, or the ring side or wire, is that conductor of a circuit which is 
associated with the corresponding member of a jack. 

12220 Negative Side or Negative Wire, Positive side or Positive Wire.— 
The negative side or wire, or the positive side or wire, is that con¬ 
ductor of a circuit which is normally connected to the corresponding 
pole of a battery. 

12221 Main Distributing Frame. —A main distributing frame is a struc¬ 
ture for terminating the permanent inside and outside wires of a 
central office and for effecting flexible junctions between them. 

12222 Intermediate Distributing Frame. —An intermediate distributing 
frame is a structure for terminating permanent inside wires of a cen¬ 
tral office and for effecting flexible junctions between them. 

12223 Switchboard. —A switchboard is an assemblage of apparatus in a 
coordinate structure for switching talking and signaling circuits. 

12224 Switchboard Section. —A switchboard section is an element or 
unit one or more of which constitutes a complete manual switchboard. 

12225 Operating Room.— An operating room is a room which contains 
a manual switchboard and associated apparatus. 

12226 Combination Current. —A combination current consists ot two or 
more currents of different characterisitics in the same circuit. As 
ordinarily used the term refers to currents whose characteristics 
are steadily maintained, as for example, a. combination of direct cur¬ 
rent and an alternating current. 

12227 Manual Ringing.— Manual ringing is ringing which is affected by 
and continues with the operation of a key. 

12228 Machine Ringing. —Machine ringing is intermittent and is caused 
to act periodically by the apparatus itself. 

12229 Superimposed Ringing Current. —A superimposed ringing current 
is a combination current for ringing, consisting of a direct and an 
alternating current. 

12230 Pulsating Ringing Current. —A pulsating ringing current is a 
current for ringing in which the succeeding impulses are separated by 
intervals approximately equal to those of the impulses themselves. 

12231 Harmonic Selective Signaling. —Harmonic selective signaling em¬ 
ploys devices tuned mechanically or electrically to the frequency of 
the ringing current, so that each device will not operate when re¬ 
ceiving current intended to operate Another device. 

12232 Multiple Harmonic Signaling. —Multiple harmonic signaling 
employs frequencies which are integral multiples of the lowest 
frequency. 

12233 Non-Multiple Harmonic Signaling. —Non-Multiple harmonic 
signaling employs frequencies which are not integral multiples of the 
lowest frequency. 

12234 “To Call”. —“To call” is to originate a telephone call. 


120 


STANDARDS OF THE A. I. E . E. 


12235 “To Dial”.—“To dial” a number is to use a dial type of calling 
device in order to control automatic switches. 

12236 “To Set Up”.—“To set up” a number is to use a key type or 
multiple lever type of calling device in order to control automatic 
switches. 

12237 Calling Device.—A calling device is an apparatus by means of 
which automatic switches are controlled for the purpose of estab¬ 
lishing a connection. 

12238 Calling Party.—A calling party is a person who originates a tele¬ 
phone call. 

12239 Called Party.—A called party is the person who answers when a 
station is called. 

12240 Reverting Call.—A reverting call is one between two stations on 
the same subscriber line. 

12241 Telephone Traffic.—Telephone traffic is the aggregate volume of 
communication handled in a given time. 

12242 “Busy”.—“Busy” is the condition of a line or an apparatus when 
it is in use. 

12243 Free.—Free is the condition of a line or an apparatus when it is 
not in use. Free is the opposite of busy. 

12244 “To Make Busy”.—“To make busy” is to cause a line or an 
apparatus to appear to be busy. 

12245 “To Release” or to “Disconnect.—“To release” or “to disconnect” 
is to terminate a telephone connection by disengaging the apparatus. 

12246 “To Clear”.— To clear” is to restore a line or an apparatus to 
the free condition. 

12247 Trunk.—A trunk is the wire connection between switching de¬ 
vices or central offices. 

12248 Trunk Circuit.—A trunk circuit is a trunk with its associated 
individual apparatus. 

12249 Trunked Call.—A trunked call is one which employs an inter¬ 
office trunk or a trunk between two switchboard positions. 

12250 Relay.—A relay is a device by means of which contacts in one 
circuit are operated by a change in conditions in the same circuit 
or in one or more associated circuits. (See Rule 4016 Standard¬ 
ization Rules, A. I. E. E., 1918). 

12251 Polar Relay.—A polar relay is a relay which operates in response 
to a change in the direction of the current in the controlling circuit. 

12252 Quick Operating Relay.—A quick operating relay is one which 
operates its contacts within a specified brief time limit. 

12253 Quick Release Relay.—A quick release relay is one which releases 
its contacts within a specified brief time limit. 

12254 Quick Acting Relay.—A quick acting relay is one which has the 
properties of both a quick operating and a quick release relay. 


TELEPHONY AND TELEGRAPHY 


121 


12255 Slow Operating Relay.—A slow operating relay is one which will 
not operate until after a specified delay. 

12256 Slow Release Relay.—A slow release relay is one which when 
operated will not release until after a specified delay. 

12257 Slow Acting Relay.—A slow acting relay is one which has the 
properties of both a slow operating and a slow release relay. 

12268 Line Relay.—A line relay is one whose coil is normally in the line 
circuit. 

12259 Cut-Off Relay.—A cut-off relay is one which when operated dis¬ 
connects from a line apparatus normally connected to it. 

12260 Relay Coil Section.—A relay coil section is one of two or more 
windings of a coil on one and the same core. The several sections 
may be concentric or placed side by side on the core. 

12261 Tension Spring.—A tension spring is one which functions to 
exert mechanical pressure but does not carry an electrical current. 

12262 Contact Spring.—A contact spring is one which takes an elec¬ 
trical part in switching a circuit. 

12263 Main Contact Spring.—A main contact spring is one which may 
switch a circuit between two or more other contact springs. 

12264 Armature Spring.—An armature spring is the first of a group to be 
moved by the armature. It may or may not be a main contact 
spring. 

12265 Plunger Spring.—Aplunger spring is the first of a group to be 
moved by the plunger. 

12266 Impulse Springs.—Impulse springs are those which act to make 
or break a circuit for the purpose of sending impulses. 

12267 Make-Before-Break Contact Springs (Abbreviation “M. B. B.”).— 
make-before-break contact springs are those in which the main 
spring touches the front contact before it breaks away from the 
back contact. Also called a continuity preserving contact. 

12268 Back Contact Spring.—A back contact spring is one against which 
the main contact spring rests when in the normal position. 

12269 Front Contact Spring.—A front contact spring is one against which 
the main contact spring rests when in the operated position. 

12270 Automatic Signaling.—Automatic signaling is affected without 
the aid of an operator. 

12271 Automatic Switch.—An automatic switch is a remote control 
device for controlling talking or signaling circuits. 

12272 Finder Switch.—A finder switch is a switch connected to one of a 
smaller number of circuits and which finds automatically a circuit 
out of a larger number of circuits from whence the signal comes. 

12273 Line Switch.—A line switch is a switch connected to one of a 
larger number of circuits from which a signal comes and which finds 
automatically a circuit out of a smaller number of circuits. 


122 


STANDARDS OF THE A. I . E. E. 


12274 Selector Switch.—A selector switch is a switch whose duty is to 
select a particular group of trunks and one trunk of the group selected. 
In particular cases, one of these functions may be omitted. 

12276 Connector Switch or Final Selector.—A connector switch or 
final selector is a switch whose duty is to establish a connection with 
the called line. . It is usually operated by the last digit or digits of 
the call number. 

12276 Switch Frame.—A switch frame is a structure for mounting an 
assembly of switching apparatus which may be integral therewith. , 

12277 Section of Switches.—A section of switches, considered from a 
trunking standpoint, is a group of adjacent switches whose banks nre 
multipled together. 

12278 Switchroom. A switchroom is a room which contains an as¬ 
semblage of automatic switches and associated apparatus. 

12279 Bank Wires.— Bank wires are those wires which multiple ad¬ 
jacent switch banks to each other. ... 

12280 Bank Cable.—A bank cable is one which connects a switch 
bank to a terminal rack. 

12281 Multiple Cable. —multiple cable is one which multiples to¬ 
gether two or more sections of switch banks by connecting together 
their terminals. 

12282 Impulse.—An impulse is any sudden change of brief duration 
produced in the current of a circuit. 

12283 Make Impulse.—A make impulse is an impulse due to a tempo¬ 
rary flow of current. 

12284 Break Impulse.—A break impulse is an impulse due to a tem¬ 
porary interruption of current. 

12286 Impulse Frequency.—:The impulse frequency is the number of 
impulses occurring per second. The reciprocal of this is the impulse 
period. 

12286 Impulse Period.—The impulse period is the period of time in¬ 
cluded between the corresponding points in periodically recording 
impulses. It thus corresponds to the period of alternating current. 

12287 Impulse Ratio. —Impulse ratio is the ratio of duration of an im¬ 
pulse to the impulse period. 

12288 Impulse Circuit. — An impulse circuit is one through which im¬ 
pulses are transmitted. 

12289 Telephone Impulse Repeater.—A telephone impulse repeater is a 
device for repeating impulses from one line circuit into another 
and for performing other duties. 

12290 Supervisory Signal.—A supervisory signal is a device for attract¬ 
ing attention of an attendant to a duty in connection with switch¬ 
ing apparatus or its accessories. This includes cord supervisory 
lamps on a manual switchboard and the supervisory lamps in an 
automatic exchange which indicates that a switch has been occu¬ 
pied but has not completed its function. 


TELEPHONY AND TELEGRAPHY 


123 


12291 Tell-Tale Signal.—A tell-tale signal is a device for locating the 
failure of some apparatus; for example, the blowing of a fuse, the 
continued drawing of heavy current by apparatus intended to re¬ 
ceive only momentary current, etc. 

12292 Alarm Signal.—An alarm signal is a sound producing device for 
attracting attention to either a supervisory or a tell-tale signal. 

12293 Amplifier.—See§13040. 

12294 Telephone Repeater.—A telephone repeater is a device for am¬ 
plifying a voice current from one line circuit into another line circuit 

12300 Telephone Receiver.—A telephone receiver is an electrically 
operated device designed to produce sound waves or vibrations which 
correspond to the electromagnetic waves or vibrations actuating it. 

12301 Microphone.—A contact device designed to have its electrical 
resistance directly and materially altered by slight differences in 
mechanical pressure. 

12302 Telephone Transmitter.—A telephone transmitter is a sound¬ 
wave-operated or vibration-operated device designed to produce 
electromagnetic waves or vibrations which correspond to the sound 
waves or vibrations actuating it. 

12303* Coefficient of Coupling of a Transformer.—The coefficient of 
coupling of a transformer at a given frequency is the ratio of the 
mutual impedance between the primary and secondary of the trans¬ 
former, to the square root of the product of the self-impedances of 
the primary and of the secondary. 

12304 Repeating Coil.—A term used in telephone practice meaning the 

same as transformer, and ordinarily a transformer of unity ratio. 

12305* Retardation Coil.—A retardation coil is a reactor (reactance 
coil) used in a circuit for the purpose of selectively reacting on currents 
which vary at different rates. 

Telegraphy 

12500 Relay.—A relay is a device by means of which contacts in one 
circuit are operated by a change in conditions in the same circuit or 
in one or more associated circuits. 

12601 Polar Relay.—A polar relay is a relay which operates in response 
to a change in the direction of the current in the controlling circuit. 

12502 Non-Polar Relay, or Neutral Relay.—A non-polar relay is a 
relay which operates in response to a change in the strength of the 
current in the controlling circuit, irrespective of the direction of the 
current. 

12603 Neutral Relay.—See non-polar relay. 

12604 Selector.—A selector is a device which performs certain func¬ 

tions such as causing an electric lamp to light, or an electric bell to 
sound, in response to a definite signal or group of successive signals 
received over a controlling circuit. . 

(12303) Single frequency voltages and currents are here supposed to be represented by 

complex numbers. Their ratio is therefore a complex number. 

(12305) In telephone and telegraph usage, the terms “impedance coil,” "inductancecoil,” 

"choke coil” and “reactance coil” are sometimes used in place of the term "retardation coil.” 





124 


STANDARDS OF THE A. I. E. E. 


12605 Direct-Point Repeater.—A direct-point repeater is a repeater 
in which the receiving relay controlled by the signals received over 
a line repeats these signals into another line or lines without the inter¬ 
position of any other repeating or transmitting apparatus. 

12606 Concentrator.—A concentrator is a traffic distributing device by 
means of which a number of telegraph or telephone lines, and connec¬ 
tions to operating instruments are brought together at one point to 
facilitate their interconnection at such times as signals or messages 
are to be transmitted from one to the other. 

12607 Transmitter.—A transmitter is a device for effecting electrical 
changes in a controlled circuit. The term transmitter is commonly 
applied principally to devices which in response to a controlling 
means effects in a main line telegraph circuit electrical changes nec¬ 
essary to send signals over the line. 

12508 Synchronous System.—A synchronous system of telegraphy is 
one in which the proper transmission and reception of signals is 
dependent upon the synchronous operation of similar commutators 
or other devices located at the sending and receiving stations of a 
circuit. 

12609 Differential Duplex.—A differential duplex is a duplex system in 
which at each station one of two portions of the receiving instrument 
is connected in series with the line wire and the other in series 
with an artificial line of such electrical characteristics that the effects 
upon the receiver of currents passing through the main and artificial 
lines, as a result of outgoing signals, are neutralized. 

12510 Bridge Duplex.—A bridge duplex is a duplex system in which 
the receiving instruments at each station is connected across two 
impedances, one in series with the line wire and the other in series 
with the artificial line in such manner that no electrical change in 
the receiver circuit is effected by outgoing signals. 

12611 Half-Set Repeater.—A half-set repeater is a repeater used for 
connecting together a simplex circuit and a duplexed circuit convert¬ 
ing them into the equivalent of a single simplex circuit. 

12512 Intermediate Current Supply.— An intermediate current supply 
is an ungrounded source of current connected in series with a line 
wire at a station other than a terminal on a ground return telegraph 
circuit. 

12613 Phantoplex Circuit.—A phantoplex circuit is a superposed circuit 
operated by alternating current over a simplex, duplex or quadru- 
plex circuit operated from direct current sources. 

12614 Spark Condenser.—A spark condenser is a condenser, with or 
without associated non-inductive resistance, connected with a 
pair of instrument contact points for the purpose of diminishing 
sparking at these points. 

12615 Current Margin.—In a non-polar simplex system, the difference 
between the current flowing through a receiving instrument when 
operated to that flowing when not operated. 


TELEPHONY AND TELEGRAPHY 


125 


12516 Margin Ratio.—In a non-polar simplex system, the ratio of the 
current flowing through a receiving instrument when operated to 
that flowing when not operated. 

12517 Percentage Margin.—In a non-polar simplex, the current margin 
expressed as a percentage of the current flowing through the relay 
when operated. 

12518 Main Circuit.—A main circuit is a major electrical circuit of a 
telegraph system and includes both transmitting and receiving devices. 

12519 Local Circuit.—A local circuit is a circuit, within the limits of 
the station, usually controlled by a receiving instrument in a main 
circuit or controlling a transmitter effecting changes in a main line 
circuit 


126 


STANDARDS OF THE A. I. E. E. 


CHAPTER XIII. 

STANDARDS FOR RADIO COMMUNICATION 

General 

This chapter has been mainly abstracted from the report of the 
Standardization Committee of the Institute of Radio Engineers, 
and is here included by permission, until further revised. For full 
particulars, see the I. R. E. Standardization Committee report. 

13000 Acoustic Resonance Device.—One which utilizes, in its operation, 
resonance to the audio frequency of the received signals. 

13001 Antenna.—A system of conductors designed for radiating or 
absorbing the energy of electromagnetic waves. 

13002 Atmospheric Absorption.—That portion of the total loss of radi¬ 
ated energy due to atmospheric conductivity. 

13003 Audio Frequencies.—Frequencies corresponding to the normally 
audible vibrations. These are assumed to lie below 10,000 cycles 
per second. 

13004 Capacitive Coupler.—An apparatus which, by electric fields 
joins portions of two radio-frequency circuits, and which is used to 
transfer electrical energy between these circuits through the action 
of electric forces. 

13005 Coefficient of Coupling (Inductive).—The ratio of the effective 
mutual inductance of two circuits to the square root of the product 
of the effective self-inductances of each of these circuits. 

13006 Direct Coupler.—A coupler which magnetically joins two circuits 
having a common conductive portion. 

13007 Counterpoise.—A system of electrical conductors forming one 
portion of a radiating oscillator, the other portion of which is the 
antenna. In land stations a counterpoise forms a capacitive 
connection to ground. 

13008 Damped Alternating Current.—A damped alternating current is 
an alternating current whose amplitude progressively diminishes. 

13009 Damping Factor.—The damping factor of an exponentially 
damped alternating current is the product of the logarithmic decre¬ 
ment and the frequency. 

Let I o = initial amplitude 

It — amplitude at the time t 
€ = base of Napierian logarithms * 

a = damping factor 
Then: I t = J 0 e~ at 

13010. Detector.—That portion of the receiving apparatus which, con¬ 
nected to a circuit carrying currents of radio frequency, and 
in conjunction with a self-contained or separate indicator, 


RADIO COMMUNICATION 


127 


translates the radio-frequency energy into a form suitable for opera¬ 
tion of the indicator. This translation may be effected either by 
the conversion of the radio frequency energy, or by means of the 
control of local energy by the energy received. 

13015 Electromagnetic Wave.—A periodic electromagnetic disturbance 
progressing through space. 

13016 Forced Alternating Current.—A current, the frequency and 
damping of which , are equal to the frequency and damping of the 
exciting electromotive force. 

13017 Free Alternating Current.—The current following any electro¬ 
magnetic disturbance in a circuit having capacitance, inductance, 
and less than the critical resistance. 

13018 Critical Resistance of a Circuit.—That resistance which deter¬ 
mines the limiting condition at which the oscillatory discharge of 
a circuit passes into an aperiodic discharge. 

13019 Group Frequency.—The number per second of periodic changes 
in amplitude or frequency of an alternating current. 

Note 1. Where there is more than one periodically recurrent 
change of amplitude or frequency, there is more than one group 
frequency present. 

Note 2. The term “group frequency” replaces the term “spark 
frequency.” 

13020 Inductive Coupler.—An apparatus which, by magnetic forces, 
joins portions of two radio-frequency circuits and is used to transfer 
electrical energy between these circuits, through the action of 
these magnetic forces. 

13025 Logarithmic Decrement.—The logarithmic decrement of an 
exponentially damped alternating current is the logarithm of the 
ratio of successive current amplitudes in the same direction. 

Note: Logarithmic decrements are standard for a complete 
period or cycle. 

Let: I n and I n +i be successive current amplitudes in the same 
direction. 

d = logarithmic decrement 
In 

Then: d = log € -- 

In +1 

13026 Radio Frequencies.—The frequencies higher than those correspond¬ 
ing to the normally audible vibrations, which are generally taken, 
as 10,000 cycles per second. See also Audio Frequencies. 

Note: It is not implied that radiation cannot be secured at 
lower frequencies and the distinction from audio frequencies is 
merely one of definition based on convenience. 

13027 Resonance.—Resonance of a circuit to a given exciting 
alternating e. m. f. is that condition due to variation of the induct¬ 
ance or capacity in which the resulting effective current (or voltage) 
in that circuit is a maximum. 



128 


STANDARDS OF THE A. I. E. E. 


13028 Standard Resonance Curve— A standard resonance curve is a 
curve the ordinates of which are the ratios of the square of the 
current at any frequency to the square of the resonant current, and 
the abscissas are the ratios of the corresponding wave length to the 
resonant wave length; the abscissas and ordinates having the same 
scale. 

13029 Sustained Radiation.—Sustained radiation consists of waves 
radiated from a conductor in which an alternating current flows. 

13030 Tuning.—The process of securing the maximum indication by 
adjusting the time period of a driven element. (See Resonance.) 

13036 Wave-Meter.—A wave-meter is a radio-frequency measuring 
instrument, calibrated to read wave lengths. 

13036 Decremeter.—An instrument for measuring the logarithmic dec¬ 
rement of a circuit or of a train of electromagnetic waves. 

13037 Attenuation, Radio.—The decrease with distance from the 
radiating source, of the amplitude of the electric and magnetic 
forces accompanying (and constituting) an electromagnetic wave. 

13038 Attenuation, Coefficient of (Radio).—The coefficient which, 
when multiplied by the distance of transmission through a uniform 
medium, gives the natural logarithm of the ratio of the amplitude 
of the electric or magnetic forces at that distance, to the initial 
value of the corresponding quantities. 

13039 Coupler.—An apparatus which is used to transfer radio-freq¬ 
uency energy from one circuit to another by associating portions 
of these circuits. 

13040 Amplifier.—An amplifier is an instrument which modifies the effect 
of a local source of energy in substantial accordance with the wave¬ 
form of the received energy, and gives out a wave of greater amplitude 
than that which it receives. 

13041 Interference.—See §12046. 

13042 Phase Angle Defect.—The phase angle defect of a condenser is the 
departure from quadrature of the phase difference between potential 
and current at terminals. This is sometimes called the phase angle 
of a condenser: although strictly speaking the phase angle of a con¬ 
denser is 90° less the phase angle defect, and is therefore exactly 90° 
when the phase angle defect is zero. 

13043 Impulse E. m. f.—An e. m. f. the effective value of which be¬ 
comes small compared with its maximum value in a time which is 
short compared with the duration of the current which it causes. 

13044 Directive Coefficient.—The directive coefficient of a transmitting 
antenna at a given distance therefrom on the surface of the earth 
or sea, for a given wave length, is the ratio of average field intensity 
within an angle of stated degrees centered about the direction of 
maximum radiation, to the average field intensity in all directions. 

13046 Directional Selectivity.—The directional selectivity of a receiving 
antenna at a given wave length is the ratio of the average e. m. f. 
induced in that antenna for waves of equal intensity coming from 


RADIO COMMUNICATION 


129 


directions comprised within an angle of stated degrees centered 
about the direction of best reception, to the average e. m. f. induced 
in the antenna for waves of equal intensity coming from all directions. 

13046 Radiation Efficiency.—The radiation efficiency of an antenna at a 
given wave length is the ratio of radiation resistance to the antenna 
resistance. 

13047 Selectivity.—The (overall) selectivity of a receiving system is 
the product of the several selectivities of that system. 

13048 Average Selectivity.—The average selectivity of a receiving 
system is the nth root of the product of the n selectivities of that 
system. 

13049* Radio-Frequency Selectivity.—The radio-frequency selectivity of 
a simple element* of a receiving system is the ratio of resonant re¬ 
sponse (in terms of effective voltage or current measured at the 
indicator) to the non-resonant response when the radio-frequency 
portions of the elements of that system are detuned by one per cent 
of the resonant frequency. 


(13049) A simple element as referred to a combination of an inductance, a capacitance 
and optionally a resistance; or their mechanical equivalent. 



130 


STANDARDS OF THE A. I. E. E. 


CHAPTER XIV. 

STANDARDS FOR PRIME MOVERS AND GENERATOR 

UNITS 

General 

14000 Regulation of Steam Engines, Steam Turbines and Internal 
Combustion Engines.—In steam engines, steam turbines and in¬ 
ternal combustion engines, the percentage speed regulation is usually 
expressed as the percentage ratio of the maximum variation of 
speed, to the rated-load speed in passing slowly from rated-load 
to no-load (with constant conditions at the supply.) 

14001 Fluctuation of Steam Engines, Steam Turbines and Internal 
Combustion Engines.—The percentage fluctuation of a steam en¬ 
gine, steam turbine or internal combustion engine, is the immediate 
percentage speed regulation corresponding to a sudden change from 
rated-load to no-load. 

14002 Regulation of Hydraulic Turbines.—In a hydraulic turbine, 
or other water motor, the percentage speed regulation is expressed 
as the' percentage ratio of the maximum variation is speed in passing 
slowly from rated-load to no-load (at constant head of water), to 
the rated-load speed. 

14003 Regulation of Generator Units.—In a generator unit, consisting 
' of a generator combined with a prime mover, the speed or voltage 

regulation shall be based upon constant conditions of the prime 
mover; i. e., constant steam-pressure, head, etc. It includes the 
inherent speed variations of the prime mover. For this reason, 
the regulation of a generator unit is to be distinguished from the 
regulation of either the prime mover, or of the generator combined 
with it, when taken separately. 

14010* Variation in Prime Movers.—The variation in prime movers 
which do not give an absolutely uniform rate of rotation or speed, 
as in reciprocating steam engines, is the maximum angular dis¬ 
placement in position of the revolving member expressed in degrees, 
from the position it would occupy with uniform rotation, and with 
one revolution taken as 360 degrees. See §4088. 

14011 Pulsation in a Prime Mover, or in the Alternator Connected 
Thereto.—The pulsation in a prime mover, or in the alternator 

(14010) If p is the number of pairs of poles, the variation of an alternator is p times 

the variation of its prime mover, if direct connected, and p n times thp variation of the 

prime mover if rigidly connected thereto in such a manner that the angular speed of the 

alternator is n times that of the prime mover. 






PRIME MOVERS. AND GENERATOR UNITS 


131 


connected thereto, is the ratio of the difference between the maxi¬ 
mum and minimum velocities in an engine-cycle to the average 
velocity. 

BIBLIOGRAPHY 
United States 

American Society of Mechanical Engineers: Boiler Code. 

Foreign 

British Engineering Standards Association: Standard Electrical 
Pressures for New Systems and Installations (Low and Medium 
Pressures); Steam Turbines for Electrical Plants; Report on 
Reciprocating Steam Engines for Electrical Purposes. 


132 


MISCELLANEOUS 


CHAPTER XV. 

STANDARDS FOR TRANSMISSION LINES 
AND DISTRIBUTION LINES 


Note: —For flash-over tests of insulators, see foot-note to §2361. 


General 


16000 Regulation of Transmission Lines, Feeders, etc—The regulation 
of transmission lines, feeders, etc., is the change in the voltage 
at the receiving end between rated non-inductive load and no- 
load, with constant impressed voltage upon the sending end. The 
percentage regulation is the percentage change in voltage to the 
normal rated voltage at the receiving end. 






PRIME MOVERS AND GENERATOR UNITS 


133 


CHAPTER XVI. 

MISCELLANEOUS STANDARDS 

HEATING DEVICES 

16000 Value of A-C. Test Voltage for Household Devices.—Heating 

• devices taking not over 660 watts, intended solely for operation 
on supply circuits not exceeding 275 volts, shall be tested with 500 
volts at operating temperature. 





/ 

» 






INTERNATIONAL ELECTROTECHNICAL 
COMMISSION RULES 























\ 
























✓ * 





































INTERNATIONAL ELECTROTECHNICAL COMMISSION 


I. E. C. RULES FOR ELECTRICAL MACHINERY 


VOLUME I. 

(Adopted at the Plenary Meeting , held in London, October , 1919) 

These rules apply to rotating machines of which the terminal pres¬ 
sure does not exceed 5000 volts or of which the rated output does not 
exceed 750 KVA., or of which the stator cores do not exceed 50 cm. in 
length axially, and to all transformers which are not water-cooled. 

PART I. GENERAL. 

I. Scope of Rules. 

0 

1. Rotating Machines. —The rules of the I. E. C. contained in this 
publication apply to rotating machines, of which the terminal pressure 
does not exceed 5000 volts or of which the rated output does not exceed 
750 kVA, or of which the stator cores do not exceed 50 cm. in length 
axially. 

2. Transformers. —These rules also apply to all transformers which are 
not water cooled. (For water-cooled transformers, see Appendix II.) 

3. Altitude. —In the absence of any information in regard to the height 
above sea level at which the machine is intended to work in ordinary 
service, this height is assumed not to exceed 1000 meters. If the machine 
is intended to work at an altitude above 1000 metres a correction to the 
temperature rise should be applied. The value for this correction has 
not yet been fixed by the I. E. C. 

4. Temperature. —In the absence of any information to the contrary, 
it is assumed that the temperature of the cooling air shall not exceed 40°C, 

II. Definitions. 

5. Rating.—(See Appendix IV.) 

6. Use of the term “ Machine." —The term “machine” is used in these 
rules in its most general sense so as to avoid the constant repetition of 
the words “machines, transformers and other electromagnetic induction 
apparatus.” 

7. Use of the term “ Power.” —It is usual to speak of a machine by its 
power. It is necessary to note that the term “power” should be used in 
the following way:— 


137 




138 INTERNATIONAL ELECTROTECHNICAL COMMISSION 


(a) For direct current generators, the electric power at the terminals 
expressed in watts (W) or kilowatts (kW). 

( b ) For alternators, the apparent power at the terminals, expressed 
in volt-amperes (VA) or kilovolt-amperes (kVA). 

(c) For motors, the mechanical power available at the shaft, expressed 
in watts (W) or kilowatts (kW). 

( d ) For transformers, apparent output at the secondary terminals, 
expressed in volt-amperes (VA) or kilovolt-amperes (kVA). 

III. I. E. C. Rating. 

8. Test Rating— The I. E. C. rating has been established as a test , 
rating which will enable an exact comparison to be made between machines, 
of different makes. 

9. Classes of Rating. —There are two classes of I. E. C. rating:— 

(a) The I. E. C. continuous rating ( see Clause 10). 

( b) The I. E. C. short time rating or limited time rating ( see Clause 12). 

10. Continuous Rating. — The I. E. C. continuous rating is the load 
which can be carried on test, under the conditions of that rating, for an 
unlimited period without the limits of the I. E. C. rules, as regards 
temperature rise, being exceeded. 

11. Service thermally equivalent to the Continuous Rating. —Any 
machine intended for continuous service on fluctuating load may be 
given for test purposes a thermally equivalent I. E. C. continuous rating, 
provided that the service for which it is intended shall not cause in any 
of its parts temperatures or temperature rises in excess of those allowed 
by the I. E. C. rules when the machine is tested under the conditions of 
its continuous rating. 

General Note re Classes of Fluctuating Load Service inserted by the 
Editing Committee.—It is desirable to distinguish between two kinds of 
fluctuating load service : — 

( i ) That in which the overload peaks can be sustained be a machine 

of ordinary construction , without modification , and without 
exceeding the limits of temperature rise allowed by these rules 
for the machine when tested under its I. E. C. continuous rating. 

(ii) That in which the overload peaks involve special provisions in 

design or construction either for mechanical or for electrical 
reasons. 

To designate this second class of service it is customary in 
Great Britain and the United States of America to employ the 
term “duty cycle rating ,” and the word “cycle" in this case 
signifies a period of time sufficiently long to include all the 
variations of load which might influence either the electrical 
construction or the mechanical construction of the machine. 

12. Short Time Rating. —The I. E. C. short time rating is the load 
which can be carried on test for the time specified in the rating, the test 
being started with the machine cold and carried out under all the con¬ 
ditions of the rating, without the limits fixed by these I. E. C. rules, as 
regards temperature rise, being exceeded. 

13. Service thermally equivalent to the Short Time Rating. —Any 
machine intended for service on loads which vary considerably may be 


INTERNATIONAL ELECTROTECHNICAL COMMISSION 139 


given for test purposes a thermally equivalent I. E. C. short time rating 
provided that the service for which it is intended shall not occasion in 
any of its parts temperatures or temperature rises in excess of those 
allowed by these rules when the machine is tested under the conditions 
of its short time rating. 

PART II. INFORMATION TO BE GIVEN WITH ENQUIRIES AND 
ORDERS FOR ELECTRICAL MACHINES. 

IV. General Information. 

Note.—T he term machine is used in these rules in its most general sense so as to avoid 
the constant repetition of the words machines, transformers and other electro-magnetic 
induction apparatus. 

14. General Information. —The inquiry or order for an electrical 
machine should give the following general information:— 

(a) The service output. 

( b ) The class of service required. 

In the absence of any indication to the contrary con¬ 
tinuous service is understood. 

(c) The maximum temperature of the cooling air in which the 
machine is intended to work when it exceeds 40°C. 

In the absence of any definite information it is under¬ 
stood that the temperature of the cooling air will not 
exceed 40 °C. 

( d ) The altitude of the place where the machine is intended 
to work if its exceeds 1000 metres. In regard to altitude, see 
Clause 3. 

(e) Any special requirements, if necessary, with regard to 
windings, methods of connection, neutral points and special 
tapping points, etc. 

(/) When the apparatus is intended to operate in parallel with 
other apparatus the fact should be stated. 

(g) Any special requirements in regard to electrical and 
mechanical details such as protective devices, cooling arrange¬ 
ments, etc. 

(Specific recommendations regarding these details will be made 
at a later date by the I. E. C.) 

V. Supplementary Information. 

15. Supplementary Information. —The above general information 
should be completed by the following supplementary information in 
regard to the particular machine forming the subject of the order:— 

16. Direct-cur rent Generator. 

Output at the terminals, in watts (W) or kilowatts (kWj. 
Pressure between terminals, in volts. 

Current, in amperes. 

Speed, in revolutions per minute. 

Method of excitation. 

17. Direct-current Motor. 

Output at the shaft, in watts (W) or in kilowatts (kW). 
Pressure between terminals, in volts. 

Current, approximate, in amperes. 

Speed at rated output, approximate, in revolutions per minute. 
Method of excitation. 


140 INTERNATIONAL ELECTROTECHNICAL COMMISSION 


18. Alternating-current Transformer. 

Frequency, in periods per second. 

Number of phases. 

Output, in voltamperes (VA), or in kilovoltamperes (kVA). 

Primary pressure between terminals, in volts. 

Secondary pressure between terminals, in volts, at no-load and 
at rated output with statement as to the power factor of 
the circuit fed by the secondary. If the power factor is 
not specified it shall be taken as 0.8. 

Secondary current, in amperes. 

For transformers intended to work in parallel, the primary 
pressure, current, and power factor on short circuit test, 
shall also be stated. 

For three-phase transformers the method of connection shall 
also be indicated in accordance with the vector diagrams 
{see Appendix I.). 

Any special requirements as to the accessibility of neutral 
points and special tapping points shall be indicated. 

Note.—W hatever, may be the nature of the transformers (step-up or step-down) the 
primary terminals are those which are connected to the source of electrical energy and the 
secondary terminals those which receive the electrical energy. 

19. Synchronous Alternator for Alternating Currents, Single or Poly¬ 


phase. 

frequency, in periods per second, 
mber of phases. 

tput between terminals, in voltamperes (VA) or kilovolt¬ 



amperes (kVA). 

Pressure between terminals, in volts, corresponding to the rated 
output. 

Power factor of the system to be supplied. If this is not 
specified it shall be taken as 0.8. 

Current, in amperes. 

Speed, in revolutions per minute. 

Excitation pressure, in volts (if the alternator is not provided 
with a special exciter). 

Maximum exciting current available, in amperes (if the alterna¬ 
tor is not provided with a special exciter). 

20. Synchronous Motor for Alternating Currents, Single or Polyphase. 

Frequency, in periods per second. 

Number of phases. 

Mechanical output at the shaft, in watts (W) or in kilowatts 
(kW). 

Current, approximate, in amperes. 

Pressure, in volts, of supply available. 

Speed, in revolutions per minute. 

Unless otherwise specified, the motor must be capable of giving 
its rated mechanical output at unity power factor. 

If the motor is required to act as a device for improving the 


INTERNATIONAL ELECTROTECHNICAL COMMISSION 141 


power factor, the value of the reactive power required shall 
- be stated. 

Excitation pressure, in volts (if the motor is not provided 
with a special exciter). 

Method of starting to be employed and source of power avail¬ 
able for this purpose. 

Maximum exciting current available, if limited. 

21. Non-Synchronous Motor for alternating currents , Single or Polyphase 

Frequency, in periods per second. 

Number of phases. 

Mechanical power at the shaft, in watts (W) or in kilowatts (kW) 

Pressure between terminals, in volts. 

Current, approximate, in amperes. 

Speed, in revolutions per 'minute, approximate, at the rated 
output. 

Rotor, whether wound or squirrel cage. 

Method of starting. 

Unless otherwise specified it is assumed that the stator receives 
the supply current. 

Starting torque in kilogrammes at one metre. 

Ratio of the starting current to the current corresponding to 
the rated output. 

Ratio of the starting torque to the torque corresponding to 
the rated output. 

The last three items are to be stated for the motor with 
its starting accessories. 

PART III. CONDITIONS TO BE FULFILLED BY ELECTRICAL 

MACHINERY. 

VI. General Remarks. 

22. General .—This section deals with the conditions to be fulfilled 
by a machine purporting to comply with the I. E. C. Rules. 

VII. Limits of Temperature and Temperature Rise. 

Temperature Limits. 

23. Table of Temperature Limits .—The following table gives the 
limits for the observable temperatures and temperature rises of windings 
and of certain parts of machines. 

The permissible temperature limits are indicated in column 1 of the 
table. 

The permissible limits of temperature rise are given in column 2. 
The temperature rises measured on any machine which has worked for 
the specified time at the output corresponding with its I. E. C. rating 
shall not exceed in any of its parts the limiting values given in column 2 
of the table. The highest permissible temperature given in column 1 
and the temperature rises, given in column 2 of the table should never 
be exceeded by a machine operating in service. 

(For exception see Clause 27.) 


142 INTERNATIONAL ELECTROTECHNICAL COMMISSION 


Temperature Limits. 


Item 

No. 

Nature of the insulation of the winding or 
name of part. 

Column 1. 
Highest permis¬ 
sible observable 
temperature. 

Column 2. 
Highest permis¬ 
sible observable 
temperature rise 
for the purpose of 
fixing the inter¬ 
national rating. 

1 

Cotton, paper or silk, non-impregnated .. 

Degrees C. 

80 

Degrees C. 

40 

2' 

“ impregnated (see 

Clause 24)... 

95 

55 

3 

Cotton, paper or silk, immersed in oil__ 

95 

55 

4 

Enamelled wire (see Clause 25). 

95 

55 

5 

Mica, asbestos, glass, porcelain, micanite 
and similar compositions. 

115 

75 

6 

Insulated windings permanently short cir¬ 
cuited ... 

100 

60 

7 

Non-insulated windings permanently short 
circuited. 

110 

70 

8 

Oil (for temperature limits, see Appendix 
II.). 

_ 

_ 

9 

Commutators, slip rings (see Clause 27).... 

90 

50 

10 

Bearings. 

80 

40 

11 

Iron core immersed in oil. 

95 

55 

12 

Iron core in contact with windings. 

Same as the windings. 

13 

Iron core not in contact with windings nor immersed in oil. 

The temperature 


and temperature rise shall not exceed that allowed for the windings themselves, 


and in no case shall the temperature and temperature rise exceed 110 C. and 

14 

and 70° C. respectively. 

Single layer windings: An increase of 5° 

C. above the temperatures given for 


items 1, 2 and 4 shall be permitted in the case of coils, revolving or stationary. 


with single layer windings when not immersed in oil. 



24. Impregnated Cotton , Paper or Silk. —An insulation is considered 
to be “impregnated” when a suitable substance replaces the air between 
its fibres, even if this substance does not completely fill the spaces between 
the insulated conductors. The impregnating substance, in order to be 
considered suitable, must have good insulating properties;' must entirely 
cover the fibres and render them adherent to each other and to the con¬ 
ductor; must not produce interstices within itself as a consequence of 
evaporation of the solvent or through any other cause;, must not flow 
during the operation of the machine at full working load at the tempera¬ 
ture limit specified; must not deteriorate under prolonged action of heat. 

25. Enamelled Wire. —When employing the temperature limits in 
the table for enamelled wire the maker must satisfy himself that the 
enamel employed is of good quality. 

26. Compound Insulations made up of Diff erent Materials. —When the 
insulation consists of layers of several different materials, the lowest of 
the temperatures permitted for the different insulating materials em¬ 
ployed ( see Clause 23) is to be adopted as the limiting temperature. 
The insulating material, even when forming the support, shall always be 
assumed as forming part of the winding. 

27. Commutators and Slip Rings. —The observable temperature and 
temperature rise of commutators and slip rings may exceed the values 



















INTERNATIONAL ELECTROTECHNICAL COMMISSION 143 

given in item 9 of the table, provided that the three following conditions 
are fulfilled:—- 

(a) The temperatures of the insulating materials in the commutator 
and on the adjoining windings shall not exceed those allowed in the table 
for the insulating materials of those parts. 

- (b) The manufacturer shall give a special guarantee that the high 
temperature attained shall not impair the commutation. 

(c) The temperature shall not be so high as to affect the quality of 
the soldered joints and the connections. 

Reference Temferature of Cooling Medium. 

28. Reference Temperature of Cooling Medium. — {a) Temperate 
Climates. In the absence of any indication to the contrary the maximum 
temperature of the air in which the machine is intended to operate in 
service shall be deemed to be 40°C. 

( b ) Cold Climates. In cold climates, when the actual temperature 
of the air in which the machine is intended to operate in service is not 
much different from 40°C. it is recommended that this conventional 
reference temperature of 40°C. should be adopted. 

(e) Tropical Climates. The question of a reference temperature for 
cooling air for machines intended to operate in service in tropical climates 
will be dealt with by the I. E. C. at a later date. 

( d ) Water Cooling {see Appendix II.) 

Permissible Limits for Temperature Rise. 

29. Permissible Limits for Temperature Rise. —The limits permitted 
for temperature rise are deduced from the values allowed for the highest 
permissible observable temperature {see Clauses 23—27) by subtracting 
therefrom 40°C. (the value assumed as that of the maximum cooling 
air temperature of the place in which the machine may be required to 
work in service) {see Clause 28). 

Temperature Measurements. 

30. Value of Temperature of Cooling Medium. —A machine may be 
tested at any convenient cooling air temperature less than 40°C., but 
whatever be the value of this cooling air temperature the permissible 
rises of temperature shall not exceed those given in column 2 of the table 
{see Clause 23). 

Corrections for variations in the cooling air temperature are not con¬ 
sidered necessary within the limits of cooling air temperature obtaining 
in general practice. 

In the case of cooling by means of forced ventilation the temperature 
of the air measured where it enters the machine shall be considered as 
the cooling air temperature. 

For all machines cooled by other means, special rules will be necessary. 
(For water cooling, see Appendix II.) 

31. Measurement of Cooling Air Temperature during Tests. —The 
cooling air temperature shall be measured by means of several thermo¬ 
meters placed at different points around and half-way up the machine 
at a distance of one to two metres, and protected from all heat radiation 
and draughts. 



144 INTERNATIONAL ELECTROTECHNICAL COMMISSION 


The value to be adopted for the temperature of the cooling air during 
a test shall be the mean of the readings of the thermometers (placed as 
mentioned above, taken at equal intervals of time during the last quarter 
of the duration of the test. 

In order to avoid errors due to the time lag between the temperature 
of large machines and the variations in the cooling air, all reasonable 
precautions shall be taken to reduce these variations and the errors 
arising therefrom. 

Methods of Measurement of the Temperatures of Machines. 

32. Measurement of the Temperatures of Machines. Two methods of 
determining the temperature of windings and other parts of machines 

are recognized:— 

(a) Thermometer method. 

(b) Resistance method.* 

♦Note.—W ith a view to brevity, the expression “method of variation of resistance of 
the winding” is replaced by the term “resistance method,” or simply “by resistance.” 

33. Thermometer Method. —In this method the temperature is de¬ 
termined by thermometers applied to the accessible surfaces of the 
completed machine. The term “thermometer” also includes thermo¬ 
couples and resistance-thermometers. 

34. Resistance Method—In this method the temperature rise, of .the 
windings is determined by the increase in the resistance of the windings 
themselves and checked by thermometers applied. to the accessible 
surfaces of the windings to ascertain whether there is any higher local 
temperature. The highest of the temperatures thus found shall be taken 
as the observable temperature. 

35. Temperature of Windings. —The temperature of windings as a 
rule shall be measured by the resistance method. The thermometer 
method alone is permitted in the following cases:— 

(a) When it is not practicable to determine the temperature rise by 
the resistance method, as for example with low resistance commutating 
coils and compensating windings, and in general in the case of low re¬ 
sistance windings, especially when the resistance of joints and connections 
forms a considerable portion of the total resistance. In this case the 
temperature limits given in the table apply without correction.. 

( b ) Single layer windings, revolving or stationary, when not immersed 
in oil. In this case an increase of 5°C. above the limits of temperature 
and of temperature rise given in the table is permitted. 

(c) When, for reasons of manufacturing in quantity the thermometer 
method is used alone, although the resistance method would be possible. 
In this case the value of the highest permissible observable temperature 
and temperature rise given in the table shall be reduced by five degrees 
except in the case of stationary field coils, when the values given in the 
table shall be reduced by the difference between resistance and thermo¬ 
meter measurements as determined on similar machines, but in no case 
shall such reduction be less than 5°C. 

36. Corrections of Measurements taken after the machine has shut 
down. —If the temperature is measured only after shut-down, the highest 
temperature attained while running shall be deduced by extrapolation 
on the time-temperature curve. 


INTERNATIONAL ELECTROTECHNICAL COMMISSION 145 


37. Measuring Temperature of Direct-Current Generators and Motors .— 
The temperature of field windings shall be measured in the manner 
described in Clauses 35 and 36. 

The temperature of the armature shall be determined as a rule by- 
thermometers placed on the windings at the hottest accessible parts, 
and when this method is employed the value of the highest permissible 
observable temperature and temperature rise shown in the table shall 
be reduced by 5°C. 

38. Measuring Temperature of Transformers. —The temperature of 
transformer Vindings shall always be ascertained by resistance. 

39. Measuring Temperature of Synchronous Alternators and Motors .-—- 
The temperature of the field windings shall always be ascertained by 
resistance. The temperature of stator windings shall be ascertained 
either by resistance or by thermometer in the manner described in the 
preceding clauses. 

40. Measuring Temperature of Non-Synchronous Motors without 
Commutators. —The temperatures of the stator and rotor shall be ascer- 
tained / in the same manner as those of the stator of a synchronous alter¬ 
nator ( see Clause 39), except in the case of a permanently short-circuited 
winding, when the thermometer method shall be employed. 

41. Coefficients of Variation of Resistance of Copper with Tempera¬ 
ture. —In the case of resistance measurements the temperature coefficient 
of copper shall be taken from the values stated in the accompanying 
table, which have been deduced from the formula 1/(234.5 + t). Thus, 
at an initial temperature t = 30°C. the temperature coefficient or in¬ 
crease in resistance per degree Centigrade rise is 1/(264.5) = 0.00378. 


Temperature of the 
windings in degrees 
C., at which the 
initial resistance is 
measured. 

Copper—increase 
in resistance per 
ohm per degree C. 

0 

0.00427 

5 

0.00418 

10 

0.00409 

15 

0.00401 

20 

0.00393 

25 

0.00385 

30 

0.00378 

35 

0.00371 

40 

0.00364 


42. When the temperature of a winding is to be determined by re¬ 
sistance, the temperature of the winding before the test measured by 
thermometer shall not differ much from that of the cooling air. 

43. Duration of Temperature Test for Continuous Rating. —For 
machines with I. E. C. continuous rating the temperature test shall be 
continued until it is evident that the maximum temperature rise attained 






146 INTERNATIONAL ELECTROTECHNICAL COMMISSION 


would not exceed the limits given in the table ( see Clause 23), if the test 
were to be prolonged until the final steady temperature were attained. 
If possible, the temperature shall be measured both while running and 
after shut-down. 

44. Duration of Temperature Test for Short-time Rating. —For ma¬ 
chines with I. E. C. short-time rating the duration of the temperature 
test shall be that corresponding to the short-time test rating as indicated 
upon the rating plate. 

At the commencement of the test the temperature of the machine must 
be practically that of the cooling air. 

VII. Dielectric Tests. 

( See Appendix III. for proposals.) 

IX. Mechanical Tests. 

(Not yet prepared.) 

X. Commutation. 

(Not yet prepared.) 

PART IV. MARKINGS. 

XI. Rating Plates. 

45. Rating Plate. —Every machine shall bear, the information neces¬ 
sary to define the limitations of the service for which it is intended. 

For this purpose it shall have in all cases a rating plate and also 
such diagrams and terminal markings as may be necessary. 

46. Information on Rating Plate. —The rating plate of a machine 
complying with the I. E. C. rules shall have a distinctive special sign 
and give the following information:— 

(a) The name of the maker. 

( b ) The maker’s machine number. 

( c ) The class of rating or the necessary information if the 

machine is intended to operate under more than one 
class of rating. 

(i d ) The altitude at which the machine is intended to work ii 
such altitude exceeds 1000 metres. 

(e) The following technical information according to the 
character of the machine:— 

In the absence of any indication in regard to the class of rating 
it is understood that the machine is intended for continuous 
service. 

47. Direct-current Generator. 

Generator—Direct-current. 

Output, in watts (W) or;in kilowatts (kW), with statement 
as to the class of rating. ; 

Pressure between terminals, in volts. 

Current, in amperes. 

Speed, in revolutions per minute. 

48. Dierct-current Motor. 

Motor—Direct-current. 

Output, in watts (W) or in kilowatts (kW), with statement 
as to the class of rating. 

Pressure between terminals, in volts. 

Current, approximate, in amperes. 

Speed, in revolutions per minute. 


INTERNATIONAL ELECTROTECHNICAL COMMISSION 147 


49. Transformer. 

Frequency, in periods per second. 

Number of phases. 

Apparent output at the secondary, in voltamperes (VA) or 
in kilovoltamperes (kVA), with statement as to the class 
of rating. 

Primary pressure between terminals, in volts. 

Secondary pressure, in volts, at no load and at rated load, with 
statement as to the power factor. 

Short circuit pressure, in volts. 

Secondary current, in amperes. 

In addition, for three-phase transformers, a vector diagram 
indicating the method of connection of the windings in 
accordance with the figures. (See Appendix I.) 

50. Alternator. 

Frequency, in periods per second. 

Number of phases. 

Apparent output, in voltamperes (VA) or in kilovoltamperes 
(kVA), with statement as to the class of rating. 

Pressure between terminals, in volts, corresponding to the 
rated output. 

Current, in amperes. 

Power factor corresponding to the rated output. 

Speed, in revolutions per minute. 

Excitation pressure, in volts. 

Maximum exciting current, in amperes. 

51. Synchronous Motor. 

Frequency, in periods per second. 

Number of phases. 

Mechanical output, in watts, (W) or in kilowatts (kW), with 
statement as to the class of rating. 

Pressure between terminals, in volts, corresponding to the 
rated output. 

Current, approximate, in amperes. 

If the motor is intended to work with a power factor different 
from unity, the necessary information to be given. 

Speed, in revolutions per minute. 

Excitation pressure, in volts. 

Maximum exciting current, in amperes. 

52. Non-Synchronous Motor. 

Frequency, in periods per second. 

Number of phases. 

Mechanical output, in watts (W) or in kilowatts (kW), with 

statement as to the class of rating. 

Pressure between terminals, in volts. 

. . ' •• • • ’* . 
Current, approximate, in amperes. 

Speed, in revolutions per minute, at rated output. 

Maximum pressure between slip rings,’in volts. 


148 INTERNATIONAL ELECTROTECHNICAL COMMISSION 


APPENDIX I. 

At the meeting of the Advisory Committee on Rating held in September, 
1913, the question of terminal marking and vector diagrams was re¬ 
ferred to Messrs. Everest and la Cour. The following rules were for¬ 
warded to the Central Office, but as they have not been submitted to 
the National Committees, the Editing Committee decided to include 
them as an Appendix only. They will, therefore, be submitted to the 
next Plenary Meeting for ratification. 

Terminal Markings for Transformers. 

1. Single-phase Transformers. —The terminals of all single-phase 
transformers shall be marked with the letter T for the high pressure side 
and t for the low pressure side. 

The neutral terminal, if provided, shall be marked by N or n. 

The letters T and t should be accompanied by subscripts 0, 1, 2, 
etc., arranged in order of progression in the same direction as the 
electromotive force in each circuit at the same instant, as shown 
in the diagram. 

If the transformer has two or more windings intended to be 
coupled in series or in parallel, the subscripts shall be single num¬ 
bers for the first of such windings (1, 2, etc.), double numbers for 
the second windings (11, 22, etc.), and so on. 

2. Polyphase Transformers. —The terminals of all polyphase trans¬ 
formers shall be marked as follows:— , 

(a) Phase Identification. The terminals of the high pressure 
and low pressure windings of any one phase shall be marked 
with the same letter, using capital letters on the high pressure 
terminals and small type letters on the low pressure terminals. 

The letters, A. B. C. a. b. c. shall be used. 

The neutral terminal, if provided, shall be marked N or n. 

( b ) Polarity Identification. The relative polarity of the corres¬ 
ponding high pressure and low pressure windings in each phase 
shall be indicated by the addition of subscripts (0) and (1) 
after the phase letters, so placed that at the instant when (in, 
for instance, phase A) the high pressure terminal marked Ai is 
positive to terminal Ao, the low pressure terminal a\ shall be 
simultaneously positive to that marked ao- 

Vector Diagrams for Polyphase Transformers. 

3. Polyphase Transformers connected together. —When two or more 
polyphase transformers are to be grouped together with their windings 
connected to the same primary and secondary systems, it is essential 
that the transformers shall correspond, not only as regards the pressures 
for which they are intended, but also as regards the exact phase relation 
of the secondary winding to the primary winding. 

4. Scope of Vector Diagrams.— All polyphase transformers shall bear 
a vector diagram which shows accurately the phase relation between 
primary and secondary terminals. To secure the correctness of such a 
diagram the following requirements shall be complied with:— 


INTERNATIONAL ELECTROTECHNICAL COMMISSION 149 


(a) The identification of each phase of the secondary winding 
with the corresponding phase of the primary winding shall 
be clearly indicated by the same terminal markings (see 
Paragraph 2 above). 

( b ) To avoid error arising from differences in methods of winding, 
the relative instantaneous polarity of primary and secondary 
windings in each phase shall be indicated at the terminals of 
the various phase windings (see Paragraph 3 above). 

5. Vector Diagrams. —The vector diagram of connections shall show 
the phase letter and the polarity marking for each phase of the windings, 
and shall show correctly how the various phases are connected together. 
But to avoid the complexity of marking both phase letter and polarity 
mark at each end of every winding vector it shall be sufficient to show 
the phase letter once, together with an arrow head to indicate polarity, 
the arrow head in every case pointing away from that end of the phase 
which has the polarity mark (0) on its terminal. 

6. The following are some typical vector diagrams which embody the 
principles laid down in these rules: 

APPENDIX II. 

This Appendix contains proposals prepared by the Advisory Com¬ 
mittee on Rating for submission to the National Committees, but not 
yet presented to a Plenary Meeting for ratification. 

1. Temperature Limits for Oil. 

Temperature limit for oil measured by thermometer. . 90°C. 

Temperature limit for the windings (measured by the 
increase of resistance) and other parts immersed in 
oil. 95 °C. 

Note. —The adoption of these temperatures implies the employment of a good oil of 
which the quality may be verified by ascertaining the flash point and measuring the de¬ 
posit produced by heating. 

The I. E. C. has not yet sufficient data to fix limiting values for the flash point or to 
prescribe the methods of measurement of the deposit. 

2. Reference Temperature of Cooling Water. —For water-cooled 
apparatus, in the absence of any indication to the contrary, the maximum 
temperature of the cooling water in service shall be deemed to be 25°C. 
at the point of entry. 

3. Temperature Limits for Water-cooled Transformers. —In the case 
of oil-immersed water-cooled transformers the limits of highest permissible 
observable temperature given in the table are to be reduced by 10°C.; 
therefore, the corresponding limits of temperature rise shown in the table 
may be increased 5°C. 

APPENDIX III. 

Dielectric Tests. 

This Appendix contains proposals in regard to Dielectric Tests pre¬ 
pared by the Advisory Committee on Rating for submission to the 
National Committees, but not yet presented to the Plenary Meeting 
for ratification. 



150 INTERNATIONAL ELECTROTECHNICAL COMMISSION 


Dielectric Tests. —The high pressure test shall be applied between the 
winding and the frame with the core connected to the frame and to the 
winding not under test, and shall be applied only to a new and completed 
machine with all its parts in place under conditions equivalent to normal 
working conditions, and unless otherwise specified the test shall be carried 
out at the maker’s works at the conclusion of the temperature test of 
the machine. 

The test pressure shall be alternating, preferably of sine wave form. 

The test shall be commenced at a pressure of less than one-third the 
test pressure and shall be increased to the full test pressure as rapidly 
as is consistent with its value being correctly indicated by the measuring 
instrument. The full test pressure shall then be maintained for one 
minute in accordance with the values as indicated in the following table:— 


Item 

No. 

Machine or Part. 

Test Pressure (R. M. S.). 

1 

Rotating machines of size less 

500 V. + twice the rated pres¬ 


than 1 kW. 

sure. 

2 

Rotating machines of size 1 

1000 V. + twice the rated 


kW to 3 kW. 

pressure. 

3 

Rotating machines of size 

1000 V. + twice the rated 


above 3 kVA. 

pressure with minimum, 



2000 V. 

4 

Field windings for synchro¬ 

10 times the excitation pres¬ 


nous generators when the 
excitation pressure does not 

sure. 


exceed 750 V. 

Minimum, 2000 V. 

Maximum, 3500 V. 

5 

Field windings for synchro¬ 
nous motors:— 



(a) When intended to be 

10 times the excitation pres¬ 


started up with the field 

sure. 


windings short circuited. 

Minimum, 2000 V. 



Maximum, 3500 V. 


( b ) When intended to be 
started up with the field 
windings separated by a 
break-up switch. 

5000 V. 


(c) When intended to be 

5000 V. when the excitation 


started up with the fields on 

pressure is less than 275 V. 


open circuit and without a 

8000 V. when the excitation 


break-up switch. 

pressure is equal to or exceeds 
275 V. 

6 

Exciter.... 

Not yet decided. 

7 

Transformers in general. 

1000 V. + twice the rated 
pressure. 














INTERNATIONA L ELECTROTECHNICAL COMMISSION 151 


Item 

No. 

Machine or Part. 

Test Pressure (R. M. S.). 

8 

Transformers for primary 
pressures over 550 V., the 
secondaries of which are for 
direct connection to public 
or private distribution sys¬ 
tems or public or private 
consumers ( i. e., secondary 
pressures less than 550 V.). 

Primary windings: 1000 V. 

+ twice the rated primary 
pressure with minimum, 
10000 V. (adopted as a pro¬ 
tection to human life). 

Secondary windings: 1000 V. 

+ twice the rated second¬ 
ary pressure. 

9 

Secondary (rotor) windings of 
induction motors not perm¬ 
anently short circuited. 

For non-reversing motors: 
1000 V. + twice the maxi¬ 
mum pressure which could 
be induced between the slip 
rings. 

For reversing motors: 1000 
V. + 4 times the pressure 
between the slip rings at 
standstill on open circuit 
with full primary pressure 
applied to tator windings. 

10 

Alternating current apparatus 
connected to a single-phase 
system of more than 300 V. 
pressure permanently 

earthed. 

< Not yet decided. 

11 

Assembled apparatus. 

When the test is made on an 
assembled group of several 
pieces of new apparatus 
each one of which has pre¬ 
viously passed its high pres- 
ure test, the test on such 
assembled group shall not 
exceed 85 per cent, of the 
lowest test pressure appro¬ 
priate for any part of the 
group. 


APPENDIX IV. 

Definitions dealing with the subject of “Rating”:— 

Gt. Britain. —The rating of an electrical machine is the output assigned 
to it by the maker, together with the associated conditions, all of which 
are marked on the Rating Plate. 

Note.—A machine may have a test rating or a service rating, or both, assigned to it, 
and marked on the rating plate. 

United States of America. —The rating of a maphine is the output 
marked on the Rating Plate and shall be based on, but shall not exceed 













152 INTERNATIONAL ELECTROTECHNICAL COMMISSION 


the maximum load which can be taken from the machine under prescribed 
conditions of test. This is also called the Rated Output. 

(The term “maximum load” does not refer to loads applied solely 
for mechanical, commutation, or similar tests.) 

France .—The rating of a machine is determined by the conditions of 
working such as speed, pressure, current, power factor, etc., as indicated 
on the Rating Plate. 

Italy .—The output of a machine is the normal or average output, that 
is to say, the load at which the machine can work under normal condi¬ 
tions. 











INDEX 


153 


INDEX 


A 

SECTION 

Abbreviations.3604 

— Photometric.11067 

Absorption, Atmospheric.13002 

Absorption Factor.11024 

Acceleration Due to Gravity, Symbol 

and Abbreviation.3604 

Acoustic Resonance Device.13000 

Active Component.3254 

Acyclic Machine.4028 

Adjustable Speed Motors.4037 

-Base Speed of..... .4038 

— Varying Speed Motors.4039 

Admittance Symbol.3604 

Advancer, Phase.4014 

— Synchronous.4015 

A. I. E. E. Rating.2224 

“Air” as a Prefix.7030 

— Blast Transformer, Temperature 

Correction for Variation of Am¬ 
bient Temperature.6311 

— Density Correction for Sphere Gap 

Spacing.2369 

-*-of Voltage....2370 

Alarm Signal.12292 

Allowances, Conventional, for Three 

Methods of Measurement.1003 

Alternating Current.3116 

A-C. Apparatus, Conditions for Effi¬ 
ciency Tests.2332 

— Commutating Machines.4017 

—- Commutator Motors, Classifica¬ 
tion of.4063 

— Convention for Vectors.3230 

— Damped.13008 

— Forced.13016 

— Free. 13017 

— Simple.3214 

— Test Voltage for Household De¬ 

vices .16000 

Alternator,.4020, 4021 

— Connected to Prime Mover, Pulsa¬ 

tion of.14011 

— Inductor.4022 

— Polyphase.4021 

— Rating.4221 

— Variation in.4088, 14010 Note 

Altitude, Correction for.2215 

-Water-Cooled Transformers. .. .6215 

Ambient Temperature.3000 

-Correction for the Deviation 

of.2311, 6311 

-for Machines Below Floor 

Line.4300 ( b) 


SECTION 

Ambient Temperature, Temperature 


Rise for any.2310 

-from an Idle Unit. 2300 (c) 

-Machines Cooled by Forced 

Draft.4300 (a) 

-Measurement of.2300 (a) ( b) 

-Water-cooled Transformers.6300 

-of Reference for Air. 1008, 2211 

-of Reference for Water. ....... 1008 

-Water Cooled Machinery.2212 

American Wire Gage.9200, 9201 

Ammeter. 8002 

Amortisseur Windings, Temperature 

of.2116, 4105 

Amplifier.,.12293, 13040 

Angular Displacement of e. m. f’s. be¬ 
tween Transformers. . . .6411 ( b ) 6418 ( b ) 

Angular Velocity.3228 

-Symbol. 3604 

Annealed Copper Standard.9050, 9202 

Annunciator Cables and Wires, Test 

Voltage.9312 (f) 

Antenna.13001 

Anti-inductive Load.3406 

Apparatus, Assembled.2357 

— Auxiliary, Losses in.4343 (c) 

— Rated above 600 Volts, Test Volt¬ 

age.7323 ( b) 

-— at 600 volts or Lower, 

Test Voltage.7323 (a) 

— Stationary Induction.6000 

— Switching and Control.7000 

Apparent Power.3238 

Arc Machines.4016 

Area, Telephone Exchange.12204 

Armature-Bearing Friction, Railway 

Motors.5338, 5339 

— Spring.12264 

Arrester, Lightning.7020 

— with Gap.7372 

Assembled Apparatus.2357 

Assurance, Factor of.9030 

Atmospheric Absorption.13002 

Attenuation (Radio), Coefficient of. . . 13038 

— Constant.12057 

— Radio.13037 

Audio Frequencies.13003 

Automatic Motorstarter.7009 

— Signaling.12270 

— Switch.12271 

— Telephone System.12201 


Automobile Apparatus, Test Voltage 1361 (/) 
— Motor and Generator Rating 

.5105, 5205, 5341 





















































































154 


INDEX 


SECTION 

Automobile Motor Brush Contact Loss 5341 
— Propulsion Machines, Observable 


Temperature Rises.5130 

— -Rating.5205 

Auto-Transformer.6010 

-for Motor Starter, Test Volt¬ 
age .7323 (c) 

— — Motor Starter.7010 

— — Voltage Test.6361 ( b ) 

Auxiliary Apparatus, Losses in.4343 ( c ) 

— Machinery, Rating.4223, 6223 

— Switch.7004 

Available Output.1600 ( b ), 2202 

Average Selectivity.13048 

Axle Bearings, Losses in.5337 

B 

Back Contact Spring.12268 

Balanced Polyphase Load.3414 

-System.3352 

Balancer.4006 

Bank Cable.12280 

— Wires. 12279 

Barometric Pressure for Institute 

Rating.2205 

Base Speed of an Adjustable-Speed 

Motor.\ • . 4038 

Bearing Friction and Windage.4337 

— —■ — — Engine Type Genera¬ 

tors... J. .4337 (c) 

-and windage, Induction 

Motors.4337 (6) 

— -— D-C. Railway Motors. . .5337 

Bearings, Temperature Limits.4109 

Bell-Rihging Apparatus, Test Volt¬ 
age.4361 (/) 

Blower, Ventilating, Losses.4343 (6) 

Booster.4003 

Bracket Systems.5007 ( d) 

Break, Impulse.12284 

Breakers, Circuit.7005 

Bridge Duplex.12510 

— Systems.5007 ( e) 

Brightness, Expression of.11012 

Brightness Ratio.11037 

Brown and Sharpe Gage.9200, 9201 

Brush Contact Loss 

4337, 6334 (6) (c) Table 402 

— Friction, Commutator and Collec-, 

tor Rings.4338 

-D-C. Railway Motors. . .5338, 5339 

— Holders, Temperature of.2116, 4109 

Brushes, Temperature of.2116, 4109 

Burden, Secondary.8031 

“Busy”.12242 

“Busy, To Make”.12244 

c 

Cable. 9004 

— Bank.12280 

— Breakdown Tests of.9314 

— Capacitance.9330 to 9334 


SECTION 

Cable Concentric, N-Conductor.9011 

— Concentric-Lay.9008 

— Designation by Cross Sectional 

Area.9201 

— Duplex.9012 

— Electrical Tests of.9300 

— Factor of Assurance.9030 

— Flexible.9402 

— Heating of.9100, 9202 Note 

— Immersion for Testing.9301 ( b ) 

— Insulation Resistance of 

. ; ..9031, 9320 to 9323 

-— Test of.9322 

— Lengths Tested.9300 

— Measurement of Capacitance of. . . .9332 

— Messenger.5005 

— Multiple.-12281 

-Conductor, Capacitance of....9334 

— -Immersion in Water.9301 ( b) 

— — — Insulation Tests of.9323 

— — Conductor, Tests of...9315 

— N-Conductor.9010 

— -Concentric.9011 

Cable Not Requiring Special Flexi¬ 
bility .9401 

— Paired, Capacitance.9333 

— Phantomed.12009 

— Rope-Lay.9009 

— Rubber Insulated.9405 

— Safe Limiting Temperature 
.9100, 9202 Note 

— Sectional Area of.9201 

— Sector.9017 

— Standard.12059 

— Test Voltage.9311, 9312 

-and Frequency... .9312 (a) 9313 

— Triplex.9015 

— Twin.9013 

Cables, Proposed Standard.9400 

“Call, To”.12234 

Call, Reverting.12240 

— Trunked.12249 

Called Party.12239 

Calling Device.12237 

— Party.12238 

Candle.11000 

— Power.11009 

— — Mean Hemispherical.11064 

— — — Horizontal.11062 

-Spherical.11063 

-Zonal.11065 

Capability (or Capacity).3504 

Capacitance Cables.9330 to 9334 

— Measurement of.9332 

— Multiple-Conductor Cables. 9334 

— Paired Cables.9333 

— Symbols., 3604 

Capacitive or Capability Coupler . . . 13004 
Capacity. 3504 

— Motor, Compared with Service 

Requirements.5502 

Cascade Converter.4011 




































































































INDEX 


155 


SECTION 

Cases, Special and Specific, General 


Comments on.1010 

Cast Grid Resistor, Temperature 

Limits.7106 

Catenary, Compound.5006 (c) 

— Simple.5006 (c) 

— Suspension.5006 (c) 

Center Contact Rail.5003 ( d ) 

Central Office.12205 

Change Speed Motor...4036 

Characteristic Curve of Luminous 

Sources.11061 

-Field-Control Motors.5402 

-Railway Motors... .5401, 5402, 5403 

— Impedance.120f54 

— Voltage Curve, Railway Motor... .5402 

Choke Coils.3078, 6015 

Circuit Braker..«..7002 

-Dielectric Tests.7323 

-Heat Test.7301 

-Interrupting Capacity.7060 

-Rating of.7201 

-Temperature Limits.7101 

— Composited.12008 

— Diplex.12012 

— Duplex.12011 

— Electric.3304 

— Equivalent.12102 

— Ground-Return.12000 

— “I” Equivalent.12104 

— Impulse.12288 

— Local.12519 

— Low-Resistance, Temperature 

Measurement of.2322 

— Main.12518 

— M etallic.12001 

— Multiplex.12014 

— Non-Phantomed.12006 

— “O” Equivalent.12106 

— “ JI” Equivalent. 12105 

— Phantom.12004 

— Phantoplex.12513 

— Polyphase.3332 

— Quadruplex.12013 

— Quarter-Phase.3328 

— Side.12005 

— Simplex.12010 

— Simplexed. 12007 

— Single-Phase. 3324 

— Six-Phase.3330 

— Subscriber Line.12216 

— Superposed... 12003 

>— “T” Equivalent.12103 

— Three-Phase.3326 

— Trunk.12248 

— T wo-Phase.3328 

— Two-Wire.<!.12002 

Circuits, Telephony and Teleg¬ 
raphy. ...' . 12000 to 12008 

Circular Inch.9200 

— Mil.9032 


SECTION 

Classes of Overhead Trolley Con¬ 
struction.5006 

Classification of Insulating Materials. .1004 

-Losses in Machinery.Table 401 

-Machinery. 4000 

“Clear, To”.! . . __12246 

Coefficient, Directive.13044 

Coefficient of Attenuation.13038 

-Coupling, Inductive.13005 

-of a Transformer.12303 

— — Reflection.11023 

-Utilization.11033 

Coil Loading.12025 

— Repeating.12304 

— Retardation...12305 

— Section, Relay.12260 

Collector Rings, Temperature Limits.4106 
-and Commutator, Brush Fric¬ 
tion .4337 

-Temperature of.2116,4106 

Combination Current.12226 

Commutating Machine, A. C.4017 

-A.C., Losses of.Table 402 

-D.C.4016 

-Losses of.Table 402 

-Synchronous.,.4018 

Commutation Limitations.4251 

— — Continuously Rated Machines 

.4251 (a) 

-Machines for Duty-Cycle 

Operation.4251 ( b ) 

Commutator Motors, A-C.4061 to 4074 

— Temperature Limits. . ..4107 

— and Collector Rings, Brush Fric¬ 

tion .4338 

Commutators, Temperature.2116, 4107 

Compensated Commutator Motor.4070 

Compensator, D.C.4006 

— Line-Drop Voltmeter.8006 

Component, Active.3254 

— Reactive.,•.3256 

Composite Line.12020 

Composited Circuit.12008 

Concentrator.12506 

Concentric Cable, N-Conductor.9011 

— Lay Cable.9008 

— Strand Cable.9007 

Condenser, Spark.12514 

— Synchronous. !.4015 

Condensive Load.3410 

Conductance, Symbol.3604 

Conducting Parts.■. .7050 

Conduction Commutator Motor.4071 

Conductivity of Copper.9202, 9050 

— Symbol.3604 

Conductor.9001 

— and Rail Systems.5000 

— Contact.5000 

— Round.9018 

— Sizes of.9200 

— Split. .9019 

— Stranded.9002 















































































































156 


INDEX 


SECTION 

Connected Load.3424 

Connection, Delta.6412 ( b) 

— Diametrical.6419 ( b) 

— Double-Delta.6419 (c) 

— Interphase, Made Outside of Case. .6413 

— Star.6412 (a) 

Connections of Transformers. .6402 to 6419 

— -Diagrammatic Sketch of... . 6404 

Constant, Attenuation.12057 

— Propagation.12056 

— Wave Length.12058 

— Current Machines, Regulation of.. .4096 

— Field Commutator Motor.4067 

— Potential Machinery, Losses 

in.4334 Note 

— Potential Transformer, Rated 

Current.6031, 6032 

— Speed D. C. Motor, Regulation of 4097 

-Motor.4035 

Consumption, Power of Auxiliary 

Devices for Lamps.11044 

— Specific, of Lamps.11045 

Contact.7051 

— Conductors.5000 

— Rail.5003 (a) 

— — Center.5003 ( d) 

-Gage.5003 ( b ) 

-Overhead.5003 ( b ) 

-Protection.5003 ( h ) 

-Third.5003 (c) 

-Underground.5003 (c) 

— Spring.12262 

-Back.12268 

-Front.12269 

-Make-Before-Break.12267 

-Main.12263 

— Voltage Regulator.6012 

Contactor.7006 

— Magnetic, Heat Tests..7302 

— Magnetic, Temperature Limits. . . .7102 

Continuous Current.3112 

-Carrying Capacity of Fuses.. . .7202 

— Loading. 12024 

— Rating.2220, 2225 

-, Railway Motors.5203 

— Surges, Lightning Arresters.7374 

— Tractive Effort.5213 

Continuously Rated Machines, Com¬ 
mutation Limitations.4251 

Control Apparatus.7000 

-Dielectric Tests.6361 ( g ) 8311 

-Phase-Failure Protection.7023 

-Phase-Reversal Protection.7024 

-Under-Voltage Protection.7022 

-Release.7021 

— Switch...7003 

Controller, Electric.7007 

Convention, Counter-Clockwise.3230 

Conventional Allowances for Three 

Methods of Temperature Meas¬ 
urement.1003 

— Efficiency. 2331 Note 


SECTION 

Converter.4008 

— Cascade.4011 

— Direct Current.4009 

— Frequency. .4012 

— Regulation.4008 

— Rotary Phase.4013 

— Synchronous.4010 

-, I 2 R Loss.4336 (c) 

Cooperating Societies.Page VI 

Copper, Conductivity of.9050, 9202 

— Constant Mass Temperature Co¬ 

efficient.9050 ( d ) 

— Standard Annealed.9050 

— Temperature Coefficient of.2331 

— Wire Tables.9203 

(5ord.9006 

Core Loss.4339, 5339 

-Induction Motors.4339 ( c) 

-Railway Motors.5339 

-Rotating Machines.4339 (a) 

-Synchronous Machines.4339 (6) 

-Due to Increased Excita¬ 
tion.4335 Note 

Cores, Temperatures of... .2116, 4108, 4109 
Correction for Cooling of Wind¬ 
ings.6320 ( c ) 

— for Deviation of Ambient Temp¬ 

eratures.2311, 6311 

— for Lay.9034, 9403 

— to Time of Shut Down.2316 

-Duration of Temp¬ 
erature Test and.1015 

Counter-Clockwise Convention.3230 

Counterpoise, in Radio Telegraphy,. .13007 
Coupler (Radio),.13039 

— Capacitive.13004 

— Direct.13006 

— Inductive.; .13020 

Coupling Coefficient.12303 

Covering of Thermometer. . .2320, 6320 (d) 
Crest Voltmeter.8004 

— Factor.3266 

Critical Resistance.13018 

Cross-Span Systems.5007 (6) 

-, Messenger.5007 (e) 

Current, Alternating.3116 

— Capacity.3504 

— Combination.2226 

— Continuous,.3112 

— Free Alternating,.3120 

— Margin.12515 

— Oscillating. 3120 

— Pulsating.3108 

— Pulsating Ringing.12230 

— Ratio of Transformer.6035, 8033 

— Superimposed Ringing.12229 

— Supply Intermediate.12512 

— Symbols..3604 

— Symmetrical.....3344 

— Transformer.8030 

-Tests.2356, 8310 


Curve, Characteristic, Photometry.. .11061 









































































































INDEX 


157 


SECTION 

Cut-off Relay.. ! . . . . 12259 

Cycle.3204 

— of Duty.2222 

D 

Damped Alternating Current.13008 

Damping.8302, 8502, 12050, 13008 

— Constant.12051 

— Factor.13009 

Data Required in Selecting Motor 

for Service.5501 

Decrement, Logarithmic.13025 

Decremeter.13036 

Defect, Phase Angle.13042 

Degree, Electric.3222 

— Magnetic.4092 

Delta Connection.6412 ( b) 

Demand.3454 

— Factor.'.3460 

— Maximum.3458 

— -Meter.8007 

— of an Installation or System.3454 

Density, Annealed Copper Standard. . .9050 
Designation of Cables by Cross-Sec¬ 
tional Area.9201 

— of Wires by Diameter or Gage 

Numbers.9200 

Detector.13010 

— Temperature, Location of.2323 

Developments of the A. I. E. E. Stan¬ 
dards .Page iii 

Deviation Factor of a Wave.3274, 4351 

— of the Ambient Temperature, Cor¬ 

rection for.2311 

Device, Calling.12237 

Diagrammatic Sketch of Connections 

of Transformer.6404 

Diametrical Connection.6419 (b) 

Dielectric Constants, Symbols.3604 

— Strength and Insulation Resist¬ 

ance.1300 to 1400 

-Test Voltage 2353 to 2355, 

4388, 6353, 6360, 6361 ( b ) 

— -Duration of Applica¬ 

tion.2355 

— — — — Frequency and Wave 

Shape.2354 

-Points of Application. . .2353 

— — Tests, Condition of Machine. . .2350 

— — — Lightning Arresters.7375 

Dielectric Strength Tests, Measure¬ 
ment of Voltage.2358 

— — Tests, Temperature at Which 

They are to be Made.2352 

— Strength Tests, Use of Voltmeters 

and Spark-gaps in.2359 

-Tests, Where Made.2351 

-Test of Cables.9310, 9311, 9314 

-of Circuit Breakers.7323 

-Machines.1301 

— — — — — Voltage Measure¬ 

ments.2359 


SECTION 

Dielectric Strength Test of Pro¬ 
tective Reactors.6361(g) 

-Switches...*.7323 

Differential Duplex.12509 

Diffused Illumination.11032 

Diffusing Surfaces and Media.11020 

Diplex Circuit.12012 

Direct Coupler.12006 

— Current.3104 

-Commutating Machines.4106 

-Compensator.4006 

— — Converter.4009 

— — Generators, Expression of 

Rating.4220 

-Machines, Losses of.Table 402 

-Railway Motors, Bearing Fric¬ 
tion and Windage.4337 ( d ) 

Direct Current Railway Motors, 

Brush Contact Loss.4338 ( b) 

— Point Repeater.12505 

— Suspension.5006 (6) 

Directional Selectivity.13045 

Directive Coefficient.13044 

Disconnect, To.12245 

Direction of Lay.9034 

Displacement, Angular... 6411 ( b ) 6418(6) 
Distributing Frame, Intermediate... 12222 
-Main.12221 

— Transformers, Tests Voltage of .6361 (a) 
Distribution Feeders, Regulation of. .15000 

— System.5031 

District, Telephone Exchange.12204 

Diversity Factor.3464 

Double-Current Generator.4007 

— Delta Connection.6419 ( c) 

Drip-Proof.7033 

-Machine.4048 


Drop, Impedance. .4089, 4090, 4091, 6052 

— Per cent.. . . .4089, 6050 

— — — in Induction Motors, 
.4089, 4090, 4091 

— — — in Transformers 6050, 
. 6051, 6052 Note 

— Impedance.4091 

— Reactance.».4090, 6051 

— Resistance.4089, 6050 

Duplex, Bridge.12510 

— Cable.9012 

— Circuit.12011 

— Differential.12509 

Duration of Heat Run.. . .2312, 2313, 2314 
Duration of Temperature Test and 

Correction to Time of Shut Down. . 1015 
Duration of Temperature Test of 

Machine for Continuous Service.2312 

Duration of Temperature Test of 
Machine with a Short-Time Rating 2313 
Duration of Temperature Test of Ma¬ 
chine having more than One Rating 2314 
Dust-Proof.7034 

— -Tight.7035 

Duty-Cycle, Equivalent Tests.2223 























































































158 


INDEX 


SECTION 

Duty Cycle Machines, Rating of.2222 

-Operation.2222 

-Machines for, Commuta¬ 
tion Limitations. 4251 ( b ) 

Dynamometer.4005 

— Regulation.4098 


E 


Effective Value.3218 

Efficiency.1500 to 1502, 3514 

— , Conventional.2351 Note, 3524 


Determination 

.2331 Note, 3524, 4342 Note 

Direct Measurement of. . . .2333 (a) ( b ) 

Directly Measured.2331 

Lamp.1102, 110434 

Normal Conditions for Test.1500 

Plant.2332 Note, 3534 

Radiation.13046 

Railway Motors.5337, 5338, 5339 

Symbol..3604 

System.3534 

Temperature of Reference 


. 1501, 1502 

—Tests, Normal Conditions for .... 2332 

---Load.2332 (b) 

-Power Factor.. . .2332 (e) 

— — — — — Temperature of Ref¬ 

erence.2332 (d) 

- -j- Wave Shape.2332 (c) 

Efficiencies Recognized.1502, 2331 

Electric Circuit.3304 

— Controller.7707 

— Degree.3222 

— Locomotives.5210 

Electromagnetic Wave.13015 

Electromotive Force, Symbols.3604 

Electrostatic Field Intensity, Symbol. 3604 

— Flux, Symbol.3604 

-Density, Symbol.3604 

Elevation of Third Rail.5003 ( b) 

-, Standard.5603 


Embedded Temperature Detector 
Method of Measuring Temperature 


. 1 .Table 100 

Enclosed Machine.4044 

-Temperature.4319, 4320 

— Ventilated Machine.4043 

Engine, Internal Combustion or 

Steam, Fluctuation of.14001 

— — —-Regulation of.14000 

— Type Generator.4027 

-Bearing Friction and Wind¬ 
age.4337 ( c ) 

Equivalent Circuit.12101 to 12106 

— Periodic Line.12019 

— Phase Difference.3262 

— Sine Wave.3260 

— Smooth Line.12018 

— Sphere Gap.7373 

Equivalent Tests, Standard Duration of 2223 
Errors of Indicating Instruments. . . .8500 


SECTION 

Exchange, Private . 12209 

- Automatic . 12210 

- Branch . 12208 

- Telephone . 12203 

Excitation for Regulation Test. . . .4390 ( b ) 
Explosion-Proof . 7036 

— — Machine . 4051 

- Slip-Ring Enclosure, Machine 

with . 4052 

F 

Factor, Crest . 3266 

— Damping...'. 13009 

— Demand . 3460 

— Deviation, of a Wave . 3274, 4351 

— Diversity . 3464 

— Load. 3438 

— of Assurance. 9030 

— Plant. 3442 

— Spherical Reduction. 11066 

— Telephone Interference. .3278 

-— Conditions of Test. 4352 (a) 

-Limiting Value. 4352 ( b ) 

Feeders, Regulation of. 15000 

Field Control Motor, Characteristic 

Curve. 5403 

— Motors, Rating of. 5204 

— Rheostat Loss. 4343 (a) 

— Windings of A-C. Generators, Test 

Voltage. 4361 (a) 

-Synchronous Machines, 

Test Voltage. 4361 (6) 

Final Selector. 12275 

Finder Switch. 12272 

Flame-Proof Machine. 4051 

Flexible-Cable, Stranding. 9402 

Fluctuation of Steam Engines, Steam 
Turbines and Internal Combustion 

Engines.14001 

Forced Alternating Current. 13016 

Form Factor. . 3270 

Frame, Distributing, Intermediate. . .12222 
-Main. 12221 

— Switch. 12276 

Fre e.. 12243 

— Alternating Current. 13017 

Frequency. 3208, 3228 

— Converter. 4012 

-Regulation. 4098 

~ Group. 13019 

— Impulse. 12286 

— Radio. 13026 

— of Test Voltage for Cables .9313 

- for Machines.2354, 4358 

Symbol and Abbreviation.3604 

Friction and Windage, Railway 

Motors .5338, 5339 

— Bearing and Windage Losses, De¬ 

termination of. .... 4337 

Front Contact Spring . 12269 

Full Mechanical Telephone System. . . 12201 
Fume-Resisting... 7032 






































































































INDEX 


159 


SECTION 

Fuse . 7015 

— Continuous Current-Carrying 

Capacity of . 7202 

G 

Gage of Third Rail . 5003 (/) 

-— Standard . 5602 

Gages for Wires . 9200, 9201 

Gap, Arrester with . 7372 

Gap Spacing for Air Density, Cor¬ 
rection of. 2369 

Gas-Proof . 7039 

— Tight. 7038 

Gearing, Losses in . 5337, 5339 Note 

General Principles.■. 1000 

Generator. 4001 

— A-C. Field Windings, Test Volt¬ 

age . : . 4361 (a) 

- Regulation of Tests, Computa¬ 
tions . 4394, 6391 

— D-C., Acyclic .4028 

— — Compound Wound . 4395 

— — Mechanical Limitations .4250 

— — Rating.4220 

— — Unipolar . 4028 

— Double Current.4007 

— Enclosed, Temperatures of. . .4319, 4320 

— Engine Type .4027 

- Bearing Friction and Wind¬ 
age.4337 (c) 

— Induction.4026 

— Regulation of .4094, 4095, 4395 

— Test Voltage.4361 (d) 

— Units, Regulation .14003 

Globe.11050 

Graded Insulation for Transformers. . .6362 
Gravity, Acceleration Due to, Symbol 

and Abbreviation.3604 

Grounded Parts .7053 

Grounding of Meters and Instruments .8110 

Ground-Return Circuit .12000 

Group Frequency.13019 

H 

Hi Lead, Location of . 6408, 6415 

Half-Set Repeater .12511 

Harmonic Selective Signaling.12231 

— Signaling, Multiple .12232 

-Non-Multiple. 12233 

Heat Run, Duration of. . . .2312, 2313, 2314 

— — Measurements of.2315 

Height, Standard, of Trolley Wire. 5601 

Hemispherical Ratio.11036 

Hevea Rubber Insulation, Test 

Voltage . 9312 (b) (c) 

High-Voltage Tests (See Dielectric 

Strength Tests) 

— Winding . 6020, 6021 

- and Low-Voltage Winding, 

Relation between . 6411 

Horse Power in Terms of Kilowatts 

. 4222 Note 


SECTION 

Hottest Spot Temperature the Prim¬ 


ary Point of Reference.1013 

— Temperatures, Limiting..1005 


Household Devices, Test Voltage 

.4361 (d), 6361 (c), 16000 

Hydraulic Turbine, Regulation of. . .14002 

I 


“I” Equivalent Circuit.12102 

Idle Unit, Ambient Temperature 

from.2300 (c) 

I. E. C. Rating.2224 

Illuminants, Rating and Output 

.11040, 11041 

Illumination.11007 

— and Photometry.11000 

— Unit of.11012 

Immersion of Cables for Testing 

..9301 (a) (6) 

Impedance, Characteristic.12054 

— Drop, Percent.4091, 6052 

— Mutual...12052 

— Self.12053 

— Sending-End.12055 

— Symbol.3604 

Impregnated Paper Insulation, Test 

Voltage.9312 ( e) 

Impulse.12282 

Impulse, Break.12284 

— Circuit.12288 

— E. M. F. 13043 

— Frequency. 12285 

— Make.12283 

— Period.12286 

— Ratio.12287 

— Repeater, Telephone.12289 

Impulse Springs. 12266 

Incandescent Lamps, Rating of.11040 

Individual Line.12217 

Induced Voltage, Testing Trans¬ 
formers by.6362 

Inductance, Symbol.3604 

Induction Apparatus, Stationary.6000 

— Generator.4026 

— Machine.4024 

— — Losses of.Table 402 

-Stray Load Losses of.4342 (6) 

— Motor.4025 

-Bearing Friction and Wind¬ 
age.4337 ( b ) 

-Core Loss.4339 (c) 

-with Explosion Proof Slip-Ring 

Enclosure.4052 

-Drop..4089, 4090, 4091 

-Phase Wound, Test Voltage.4361 ( c ) 

— — Rotor, Polyphase, I 2 R 

Loss.4336 ( b ) 

— Voltage Regulators.6013 

Inductive Coupler.13020 

— Interference.12298 

— Load.3408 

Inductor.3070 





























































































160 


INDEX 


SECTION 

Inductor Alternator.4022 

Information on Rating Plate.2401 (a) 

In-Phase Component of Current or 

Voltage.3254 

Instantaneous Values, Symbols for. . .3608 

Institute Rating.2204 

Instrument. 8001 

— Current Transformers on Open 

Secondary Circuit.8111 

-Closed Secondary Cir¬ 
cuit.8112 

■— Grounding of.8110 

— Indicating, Errors of.8500 

— Period of.8020 

— Rating Limitations of the Circuits 
.8200, 8202 

— Recording. 8003 

— Standard Temperature of Refer¬ 

ence for.8201, 8203, 8301 

— Torque of..., .8501 

— Transformers.8030 

— — Dielectric Tests of.8312 

— Windings, Temperature Rise of. . .8203 
Insulating Material, Parts Adjacent 

to.2116 

-not Adjacent to.2116 

-Classification of.1004 

Insulation, Graded, Transformers 

with...... 6363 

— Resistance.2380 

-Dielectric Strength and. 1300 to 1400 

-Expression of.9320 

-of Cables.9031, 9320 to 9323 

-Machines.2381,2382 

-Significance of.1400 

— — Multiple-conductor Cab’es.9323 

-Test, Voltage for.2381 

-Minimum Values.2382 

— Thickness of, for Wires and Cables. 9405 
Insulations of More Than One Class, 

Permissible Temperatures with.2104 

Integrated-Demand-Meter.8007 (Jo) 

Intensity of Illumination.11006 

-Magnetization, Symbol.3604 

Interconnected Polyphase Windings, 

Voltage Test.2353 (Jo) 

Interference.13041 

Intermediate Current Supply.12512 

— Distributing Frame.12222 

Internal Combustion Engines, Fluc¬ 
tuation of.14000 

-Regulation of.14001 

Interurban Railways, Standard 

Height of Trolley Wires.5601 

Integrated-Demand Meter.8007 (Jo) 

Interphase Connection.6413 

Interrupting Rating.7060 

12 R Loss.4336 (a) 

-Polyphase Induction Motor- 

Rotors.4336 ( b) 


SECTION 

K 


Kilovolt-Ampere Rating.4221, 6221 

Kilowatt Rating.4220, 4222 

Kinds of Rating.2220 


L 


Lag . 3224 

Lagged-Demand Meter.8807 ( c) 

Lambert.11013 

Lamp Accessories . 11048 

— Characteristic Curve . 11061 

— Efficiency . 11042, 11043 

— Life Tests.11046 

— Mean Hemispherical Candle- 

Power . 11064 

— — Horizontal Candle-Power.11062 

— — Spherical Candle-Power . 11063 

— — Zonal Candle-Power . 11065 

Lamp, Performance, Curve.11060 

— Specific Consumption.11045 

— Specific Output, Expression of. . .11043 

— Spherical Reduction Factor .11066 

— Comparison of. 11047 

Lay . 9033 

Lay, Correction for. 9403 

— Direction of . 9034 

— of Strands . 9034 

Lead . 3224 

— Location of Hi . .. ;. 6408, 6418 

— Neutral. 6403 (b) 

Leads, Marking of Full Winding. 6410 

— Transformer, Marking of . 6403 (a) 

— Six Phase, Marking of. 6417 

- Numbering of. 6405 

- Relation of Order of 

Numbering . 6406 

— Tap. 6412, 6419 

Life Tests of Lamps. 11046 

Lightning Arresters . 7020 

-Performance and Test. .7371 to 7374 

-Rating. 7205 

Limiting “Hottest Spot” Tempera¬ 
tures. 1005 

— Observable Temperature of 

Oii. 1007, 2232, 6202 

— -Shunts. 8101 

- and Temperature Rises for 

Transformers Using Class 

A Insulation . 6201 

-Rises. 1009, 2230 

-Temperatures. 1006 

— Value, Telephone Interference 

Factor.4352 ( b ) 

Limitations, Commutation . 4251 

Limitations of Stability. 4252 

Limits, Temperature, Exception to 

Method 1. 4319 

-2. 4320 


-in Special Cases, Comments on. 1012 

Line Characteristics, Telephony and 

Telegraphy.12054 





























































































INDEX 


161 


SECTION 

Line Circuits, Telephone and Tele¬ 


graph.12000 to 12009 

— Composite.12020 

— Drop Voltmeter Compensator.8006 

— Equivalent Periodic.12019 

-Smooth.12018 

— Individual.12217 

— Loaded.12021 

— Party.12218 

— Periodic.12017 

— Relay.12258 

— Series Loaded.12022 

— Shunt Loaded.12023 

— Smooth.12016 

— Switch.12273 

Linear Capacitance.9330 

— Electrical Constants.12015 

— Insulation Resistance.9320 

Load, Anti-Inductive.3406 

— Balanced Polyphase.3414 

— Condensive.3410 

— Connected.3424 

— Efficiency Tests,.2332(b) 

— Factor.3434, 3435 

— Inductive.3408 

— Losses.6337 

— Losses, Stray.4342 

— Maximum.3508 

— Non-reactive.3406 

— Reactive. 3404 

Loaded Line.12051 

Loading, Coil.12025 

— Continuous.12024 

Loading of Telephone Lines. 12051 to 12054 

— Transformers for Temperature 

Tests.6317 

Loads, Momentary, Continuously 

Rated Machines.4251 (a), 4252 

Local Central Office.12207 

— Circuit.12519 

Location of Hi Lead.6415 

Locomotive Speed.5214 

— Continuous Tractive Effort.5213 

— Electric.5210 to 5214 

— for Intermittent Service.5213 

— Normal Tractive Effort.5212 

— Rating.5210 

— Weight on Drivers.5211 

Logarithmic Decrement.13025 

Loop, Subscriber.12215 

Loss. Brush-Contact I 2 R .4341 

— 12 R . 4336 

Losses, Auxiliary Apparatus.4343 (c) 

— Axle-Bearing and Gearing.5337 

Losses, Bearing Friction and Windage4337 

— Brush Friction.4338 

— Classification of.4334 

— Due to Ventilating Blower.4343 (&) 

— Evaluation of.4335 Note 

— Field-Rheostat.4343 (a) 

— Gearing and Axle Bearing.5337 


SECTION 

Losses in Constant Potential Machin¬ 


ery.4335 Note 

— in Field Rheostats.4343 ( a ) 

— in Machines.4335 

— in Railway Motors.5337 to 5339 

— in Transformers.6336, 6337 

— in Ventilating Blower.4343 ( b ) 

— Indeterminable.Table 402 

— Indeterminate.4342 Note 

— Induction Machines.Table 402 

— Load.6337 

— Miscellaneous.4343 

— No Load...6336 

— Stray Load.4342 

— Synchronous Converter.4336 (c) 

— — Machines.Table407 

— Table of.Table 401 

— Transformers.6334 to 6337 

— Ventilating Blower.4343 (6) 

Low-Voltage Release.7021 

-Protection.7022 

-Winding.6020, 6021 

-and High-Voltage Winding, 

Relation between.6411 

Lumen.11010 

Luminosity.11004 

Luminous Efficiency.11005 

— Flux.11000, 11010 

— Flux, Unit of.., .11012 

— Intensity.11016 

— Sources, Comparison of.11047 

Lux.11012 

M 

Machine, Acyclic.4028 

— A-C. Commutating.4017 

— Automobile Propulsion, Ratings. . .5205 

-Temperature Limits.5130 

— Below Floor Line, Measurement of 

the Ambient of.4300 ( b) 

— Connected to Permanently 

Grounded Single-Phase Systems 
Test Voltage.4361 (c) 

— Continously Rated, Commutation 

Limitations of.4251 (a) 

— Cooled by Forced Draft, Measure¬ 

ment of the Ambient of.4300 (a) 

— Cooled by Means Other than Air 

or Water.2213 

— Drip-Proof...4048 

— Duty,Cycle, Commutation Limi¬ 

tations.4251 ( b) 

-Rating of. 2222 

— Efficiency.3514, 3524 

— Enclosed.2332 ( b ) 

-Ventilated.4043 

— Explosion-Proof.4051 

— Flame-Proof.4051 

— for Continuous Service, Duration 

of Temperature Test for.2312 

— for Use on Circuits of 25 Volts on 

Lower, Test Voltage.4361 ( b ) 











































































































162 


INDEX 


SECTION 

Machine having more than One Rat¬ 
ing, Duration of Temperature 


Test for.2314 

— Induction.4023 

— — Stray Load Losses.4342 ( b) 

— Losses to be Considered in.4335 

— Metallic Parts, Temperatures of. .2116 

— Rotating Electric Losses in. .Table 402 

— Not Cooled by Air or Water.2213 

— Open.4041 

— Partly below Floor Line, Ambient 

Temperature.4300 ( b ) 

— Protected.4042 

— Rating.3508 

— — Principle of.1600 

— Ringing.12228 

— Rotating Electric Losses in. . . Table 402 

— Self-Ventilated.4046 

— Semi-Enclosed.4043 

— Separately Ventilated.4045 

— Substation, Railway, Nominal 

Rating. 5201 

— -Temperature Limits.5120 

— Synchronous.4019 

— — Commutating.4018 

-Core Loss.4339 ( b ) 

— — Field Windings, Test Volt¬ 


age.4361 if) 

— — Stray Load-Losses.4342 (a) 

— Totally Enclosed.4044 

— Unipolar.4028 

— Water-Cooled.4047 

— with Explosion-Proof Slip-Ring 

Enclosure. 4052 

— with a Short-Time Rating, Dura¬ 

tion of Temperature Test of. . . 2313 

— with Small Ventilating Apertures. .4316 

Machines, D-C. Commutating.. . .4016 

Machinery, Auxiliary, Rating.4223 

— Cooled by Ventilating Air from 

Distance.2300 Note 

—- for High Ambient Temperatures 2331 ( d ) 

— Rotating Electric, Classification. . 4000 

— Outdoor, Exposed to Sun’s Rays. .2214 

— Water-Cooled, Ambient Tempera¬ 


ture of Reference for.. ...2212 

Magnet Brake.7052 

Magnetic Contactors, Heat Tests.7302 

— — Temperature Limits.7102 

— Degree.4092 

— Field Intensity, Symbols and Ab¬ 

breviations .3604 

— Flux, Symbols.3604 

— — Density, Symbols.3604 

Magneto Voltage Regulator.6014 

Magnetomotive Force, Symbol.3604 

Main Circuit. 12518 

— Contact Spring.12263 

— Distributing Frame.12221 

Make-Before-Break Contact Springsl2267 

— Impulse.12283 

Manual Ringing.12227 


SECTION 

Manual Telephone System.12200 

Margin, Current.12515 

— Percentage.12517 

— Ratio.12516 

Marked Ratio of Instrument Trans¬ 
formers.8034 

Marking of Full Winding Leads.6410 

— of Leads.6403 

— of Switchboard Shunts.8503 

Mass Resistivity.9050, 9202 

— Symbol and Abbreviation. .. 3604 

Master-Switch.7002 

Materials, Classification of Insulating. 1004 
Maximum Demand.3458 

— Equivalent Line.5003 ( b) 

— Load.3508 

— Temperature, Wires or Cables.9100 

— — Temperature Rise in Service. .'4110 

— Values,Symbols for.3608 

Mean Hemispherical Candle-power. .11064 

— Horizontal Candle-power.11060 

— Spherical Candle-power.11063 

— Temperature.2300 (b) 

— Zonal Candle-power.11065 

Measurement of Ambient Tempera¬ 
ture .2300 

— Temperature during Heat Run. . . .2315 

—- — Method Used for Stators.4321 

— .Method to Be Employed.1011 

Mechanical Degree.4092 

— Equivalent of Light.11003 

— Limitations.4250 

— Power, Where Measured.2333 (c) 

Megohms.9320 

— Constant.9321 

Messenger Cross-Span Systems.. . .5007 (c) 

— Suspension.5006 (c) 

— Wire or Cable.5005 

Metallic Circuit.11001 

— Parts of Machines, Temperature of .2116 

Meter.8000 

— Demand.8007 (a) 

— Dielectric Tests.8312 

— Grounding of.8110 

— Power-Factor.8002 

— Rating Limitations of the Cir¬ 

cuits.8200, 8202 

— Reactive-Factor.8002 

— Standard Temperature of Refer¬ 

ence for.8201, 8203, 8301 

— Torque of.8501 

— Watthour.8002 

— Windings, Temperature Rise of... .8203 

Method of Measurement to Be Em¬ 
ployed .1011 

— of Temperature Measurement Used 

for Stators of Machines.4321 

Methods of Measurement of Regula¬ 
tion . 4394 

— of Temperature Measurement 1001, 1002 

— -Conventional Allow¬ 

ances for.1003 



























































































INDEX 


163 


SECTION 

Microfarads, Constant.9331 

Microphone.12301 

Mil, Circular.9032 

Millilambert.11013 

Milliphot.11012 

Minimum Values of Insulation Re¬ 
sistance.2382 

Moisture Resisting.7039 

Momentary Loads, Continuously 

Rated Machines.4252, 5251 ( d ) 

Motor.4002 

— Adjustable Speed.4037 

— — -Varying Speed.4039 

— Automobile, Brush Contact Loss..5341 

— -Booster.4003 

— Capacity, Comparing with Service 

Requirements.5502 

— Change-Speed..._.4036 

— Compensated Commutator.4070 

— Conduction Commutator.4071 

— Constant Field Commutator.4067 

— Constant Speed.4035 

-Regulation of.4097 

— -Converter.4011 

— Enclosed, Temperature of. .4319, 4320 

— Field Control, Rating of.5204 

— -Generator Set.4004 

— -Generator, Regulation.4098 

— Induction.4025 

-Bearing Friction and Wind¬ 
age..4337 (6) 

-Core Loss.4339 (c) 

-Phase-Wound Rotors, Test 

Voltage.4361 ( c ) 

— Mechanical Limitations.4250 

— Multispeed.4036 

— Neutralized Commutator. .. .4069 

— Polyphase Commutator.4062 

— Railway, Armature Bearing Fric¬ 

tion .5338, 5339 

-Brush Friction.5338, 5339 

-Continuous Rating.:.5203 

-Core Loss.5339 

-Characteristic Curve.. .5401 to 5403 

— — Efficiency.5338, 5339 

— — Losses in.5337, 5338, 5339 

— — Nominal Rating. . . v ..5202 

— — Rating of.5202, 5203 

-Selection of.5501 

-Service Capacity.5502 

-Stand Test Temperature 

Rise.Table 802 

— — Windage Losses.5338, 5339 

— Rating.4222, 5203 

— Repulsion Commutator.4074 

— Rotor-Excited Commutator.4065 

— Single-Phase Commutator .4061 

— Small, and Generators, Test Volt¬ 

age. . . .4361 ( d) 

— Speed Regulator.4097 

— Stalling Torque of.4250 ( c) 

— Stator-Excited Commutator.4064 


SECTION 

Motor Stator- and Rotor-Excited 


Co mmutator.4066 

— Synchronous.4023 

— Transformer-Conduction Commu¬ 

tator.4073 

-Commutator...4072 

— Varying Field Commutator.4073 

--Speed.4039 

Motorstarter.7008 

— Automatic.7009 

— Auto-transformer.7010 

Motor-Vehicle Ratings.5105, 5205 

Motors, A-C., Commutating, Classi¬ 
fication.4017, 4061 to 4071 

Multidirectional Illumination.11031 

Multiple Cable.12281 

— -Conductor Cable.9010, 9011 

-.Capacitance.9334 

-, Immersion for Test.9301 ( b ) 

-, Insulation Resistance. . . .9323 

-Cables, Tests.9315 

— Harmonic Signaling.12232 

Multiplex Circuit.12014 

Multi-Speed Motors.4036 

Mutual Impedance.12052 

— Inductance, Symbol.3604 

N 

N-Conductor Cable.9010 

— — Concentric Cable.9011 

Needle-Gap Spark-Over Voltages.2365 

Negative Side.12219 

— Wire.12219 

Neutral Lead.6403 (b) 

— Relay..12503 

Neutralized Commutator Motor.4069 

No-Load Losses.6336 

Nomenclature, General.8002 

Nominal Rating.6236 

-, Railway Motors.. .5202 

-Substation Machines.5201 

— Tractive Effort...'..5212 

Non-Multiple Harmonic Signaling. . .12233 

— -Phantomed Circuit.12006 

— -Polar Relay.12502 

— -reactive Load.3406 

Notation.3604 

Number of Conductors or Turns, 

Symbol.3604 

Numbering of Leads, Order of.6405 

-Relation of Order of.6406 

o 

“O” Equivalent Circuit.12106 

Observable Temperatures, Limiting. . .1006 

-of Oil, Limiting.1007, 2232 

-Rise the Working Standard .... 1014 

— — Rises, Limiting.1009, 2230 

Office, Central.12205 

— Local Central.>.12207 

— Toll Central.12206 

“Oil” as a Prefix.7031 






































































































164 


INDEX 


SECTION 

Oil Cup.2301 

— -Immersed Transformers, Temper¬ 

ature Measurement. ..6320 (c) 

— Limiting Observable Temperature 

of.1007, 2232 

Open Machine.4041 

Operating Room.12215 

Operation, Duty-Cycle.2222 

— Parallel.6409, 6414 

Oscillating Current.3120 

Other Approved Standards.Page v 

Outdoor Machinery Exposed to Sun’s 

Rays.2214 

Output, Available.1600 ( b ), 2202, 3504 

— Specific of Electric Lamps.11043 

— of Illuminants.11040 

— Rated.3508 

Over-Speeds.42*50 (a), (b) 

Overhead Construction.5006 (a) 

— Contact Rail.5003 ( b) 

P 

Pads for Thermometers. . . .2320, 6320 ( d ) 

Pair, Twisted.9016 

Paired Cables.9333 

Paper, Impregnated, Working Tem¬ 
perature.9100, 9202, 6409 

Parallel Operation.6414 

Parts, Conducting.7050 

— Grounded.7053 

— of Machines, Temperatures 

of.2116, 4109 

Party Called.12239 

— Calling.12238 

— Line.12218 

Pay Station. 12213 

Peak Factor.3266 

— Power.3434 

Per Cent Impedance Drop.4091 

— — Reactance Drop.4090 

— — Resistance Drop.4089 

Percentage Margin...12517 

— Saturation.4086 

Performance Curve, Lamp.11060 

Period.3206 

— Impulse.12286 

— of an Instrument.8020 

Periodic Line.12017 

Permeability, Symbol.3604 

Permissible Temperatures with Insu¬ 
lation of More Than One Class 2104 

Phantom Circuit.12004 

Phantomed Cable.12009 

Phantoplex Circuit.12513 

Phase.3222, 3228 

— Advancer.4014, 4015 

— Angle Defect..13042 

— Converter.4013 

— Difference.3224 

-Equivalent...,.3262 

— Displacement, Symbols...3604 

— Failure Protection.7023 


SECTION 

Phase Modifier.4014 

— Reversal Protection.7024 

— Single.3324 

— Six.3330 

— Three.3320 

— Wound Rotors, Dielectric Tests. . . .4361 

Phot.11012 

Photometric Units and Abbrevia¬ 
tions .11067 

JX Equivalent Circuit.12105 

Plant Efficiency.2332 Note, 3524 

— Factor.3442 

Plate, Rating. 2401 

Points of Application of Voltage for 

Test.2353 

Polar Relay.12251, 12501 

Polarity.6407 

Pole Tips, Temperature of.2116, 4109 

Polyphase Alternator.4021 

— Circuit.3332 

— Commutator Motor.4062 

— Induction-Motor Rotor, I 2 R 

Loss.4336 ( b ) 

— System, Balanced.3352 

— — Symmetrical.3344 

Positive Side..12220 

— Wire.12220 

Potential Difference, Symbols.3604 

— Transformer.8030 

Power.3234 

Power, Apparent.3238 

— Consumption of Auxiliary De¬ 

vices .11044 

— Factor.3242 

-and Regulation.4390 (a) 

— — Efficiency Tests.2332 ( e ) 

— — Meter.8002 

— in A-C. Circuits.3234 

— Peak.3434 

— Symbols.3604 

Preface to 1921 Edition.Page ii 

Primary Winding.6020, 6021 

Prime Movers, Fluctuation of.14001 

— — Pulsation in.14011 

-Regulation of.14000 

-Variation in.14010 

Principles, General. t .1000 

Private Automatic Exchange.12210 

— Branch Exchange.12208 

— Exchange.12209 

Propagation Constant.12056 

Protected Machine.4042 

Protection against Short Circuit.2120 

— of Thermometers.2320, 6320 ( d ) 

— Third Rail.5003 (A) 

Protective Reactor.3078, 7019 

-Rating.6204 

Pulsating Current.'. .3108 

-Ringing.12230 

Pulsation in Prime Mover.14011 

Purpose of the A. I. E. E. Standards. Page ii 
Putty for Thermometers.2320, 6320 (d) 














































































































INDEX 


165 


SECTION 

Q 

Quadded Cable.12009 

Quadrature Component of Current or 

Voltage.3256 

Quadruplex Circuit.12013 

Quantity of Electricity, Symbols.3604 

Quarter-Phase Circuit.3328 

Quick Acting Relay.12254 

— Operating Relay.12252 

— Release Relay.12253 


R 


Radiant Flux.11000 

Radiation Efficiency...13046 

Radiation, Sustained.13029 

Radio Frequencies.13026 

— Frequency Selectivity.13049 

Rail, Contact.’. . . .5003 ( a ) 

-Center.5003 (d) 

-Overhead.5003 ( b ) 

— Center Contact.5003 (d) 

— Overhead Contact.5003 ( b) 

— Third.5003 (c) 

-Elevation of.5003 (g) 

-Gage of.5003 (f) 

-Protection. 5003 ( h) 

-Standard Elevation of.5603 

-— Gage of.5602 

— Underground Contact.5003 ( e ) 

Railway Motor.. .5101 Note, 5202 to 5204, 

.5401 to 5403, 5337 to 5339 

-- Armature Bearing Loss.. .5338, 5339 


-Capacity and Requirements 

of... .3078, 5502 Note, 6015, 7019 
-Characteristic Curves. . 5401 to 5403 


-Voltage Curve.5402 

-Continuous Rating of.5203 

— — Bearing Friction and Windage.5337 

-Brush Friction.5338, 5339 

-Continuous Rating.5203 

— — Core Loss.5339 

-Efficiency and Losses of 


.5337, 5338, 5339 

-Field Control, Rating of.5204 

-Friction and Windage. .. .5338, 5339 

-in Continuous Service, Temp¬ 
erature Limits.5101 

— — Losses.5337, 5338, 5339 

-Nominal Rating.5202 

-Selection of.5501, 5502 

-Stand Tests of;.5502 

— — Temperature Limitations of. .. .5101 


-Temperature Rise in Continu¬ 
ous Service Compared to 


Stand Test.5502 

-Windage Losses.5338, 5339 


-Temperature Limits, in Contin¬ 
uous Service...5101 


—■ Substation Machines and Trans¬ 
formers, Nominal 
Rating of. 


5201 


SECTION 

Railway Substation Machines and 
Transformer, Temperature Limits 

of.5120 

Rated Current of Constant-Potential 

Transformer.6031, 6032 

— Output.3508 

— Primary Voltage of Constant-Po¬ 

tential Transformer.6032 

Rating.1600, 3508 

— Alternators.4221 

— A. I. E. E.2224 


— Automobile Propulsion Machines. . 5205 


— Auxiliary Machinery.4223 

— Circuit Breakers.7201 

— Continuous.2220 

-Implied.2225 

-Railway Motors.5203 

— D-C. Generators.4220 

— Duty Cycle Machines... .2222, 4251 ( b ) 

— Electrical Machines.3508 

— Expression of.2202 

— — — in Kilovolt-Amperes.4221, 6221 

-Kilowatts..4220, 4222 

— Field Control Railway Motors.5204 

— Fuses.7016 

— Incandescent Lamps.11040 

— Institute.2204 

— I. E. C.2224 

— Interrupting.7060 

— Lightning Arresters.7205 

— Limitation of Circuits of Meters 

and Instruments.8202 

— Locomotives.5210 

— Meter.8200 

— Motors.4222 

-Expression of, in Kilowatts.4222 

— Nominal.6236 

— — of Railway Motors.5202 

-Substation Machines 

and Transformers.5201 

— Plate, Distinctive Marking. . . .2401 () 

-Marking... >...2401 

-for Various Ratings.2401 ( c) 

— — Marking, Principle of.1600 ( a ) 

-Significance of Marking.2401 ( c ) 

— Protective Reactors...6204 

— Short-Time.2221 

-Railway Motors.5202 

— -Standard.2223 


— Stationary Induction Apparatus 


(Other Than Transformers).6223 

— Switches.7201 

— Transformers.6221 

Ratio, Current.6035, 8033 

— Impulse.12287 

— Marked.8034 

— of Transformer.6033 

— Voltage.6034, 8032 

— Volt-Ampere.6036 

Reactance, Coils.3078, 6015 

— Drop, Per Cent....4090, 6051 

— Symbols.3604 






























































































166 


INDEX 


SECTION 


Reactive Component . 3256 

— Factor . 3250 

— — Meter . 8002 

— Load. .. 3404 

— Voltamperes . 3246 

Reactor . 3078, 6015 

— Protective . 7019 

— Protective, Rating of. 6204 

- Test Voltage. 6361 (g) 

Receiver, Telephone. 12300 

Recording Instruments. 8003 

Redirecting Surfaces and Media . 11021 

Reduction Factor, Spherical . 11066 

Reference, Primary Point of, Hottest 

Spot, the. 1013 

Reflection Factor. 11023 

Reflector. 11048 

Regulation. 2390 (c), 3535, 4094 

— A-C. Generators. 4394 

Regulation and Excitation . 4390 ( b ) 

-Frequency. 2390 (a) 6390 ( a ) 

-Power Factor . 4390 (a) 6390 ( b) 

-Wave Form .. 2390 ( b) 

— Computation and Tests . 6391 

— Conditions for Tests of . 2390, 4390 

— Constant-Current Machines . 4096 

-Potential A-C. Generators . 4095 

-— Transformers .6053 

-Speed Motors .4097 

— Converters, Dynamometers, Mo¬ 

tor-Generators and Frequency 
Converters. 4098 

— D-C. Generators. 3094, 4095 

— Excitation.4390 (6) 

— Generator Unit. 14003 

— Hydraulic Turbine.14002 

— Methods of Measurement. 4394 


— Steam Engines, Turbines, and 

Internal Combustion Engines... 14000 


— Temperature.2390 (c) 

— Tests.2390 (a), 6390 (a) 

— Transformers.6391 (a) ( b ) 

— Transmission Lines, Feeders, etc. . 15000 

Regulator, Contact Voltage.6012 

— Induction Voltage.6013 

— Magneto Voltage.6014 

— Voltage.6011 

Relative Weighing of Components.4352 

Relay.7016, 12250 

— Coil Section.12260 

— Cut-Ofl.12259 

— Dielectric Tests.7323 

— Heat Tests.•.7301 

— Line.12258 

— Neutral.12503 

— Non-Polar.12502 

— Polar.12251 

— Quick Acting.12254 

-Operating.12252 

— — Release.12253 

— Slow Acting.12257 

-Operating.12255 


SECTION 

Relay Slow Release.12256 

— Temperature Limits.7101 

“Release, To”.12245 

Reluctance, Symbol.3604 

Repeater, Direct Point.12505 

— Half-Set.12511 

— Telephone.12294 

-Impulse. 12289 

Repeating Coil.12304 

Repulsion Commutator Motor.4074 

Resistance, Coefficient of Standard 

Annealed Copper.9050 

Resistance Drop, Per Cent.4089, 6050 

— Insulation, and Dielectric 

Strength. 1300 to 1400 

— Insulation, Expression of, Wires 

and Cables..9320 

-of Conductor.9031 

-of Machines.2381, 2382 

— Lightning Arresters.7371 

— Method of Measuring Tempera¬ 

ture.2322, 6320 ( e ) 

— Standard Annealed Copper.9050 ( b ) ( e) 

— Symbols.3604 

Resistivity.3020 

— Symbol and Abbreviation.3604 

Resistor.3064, 7018 

— Cast Grid....7106 

Resonance.13027 

— Curve.13028 

— Device, Acoustic.13000 

Retardation Coil.12305 

Reverting Call. 12240 

Rheostat.3064, 7018, 7106 

— Field, Losses.4343 (a) 

Ring Side.12219 

— Wire.12219 

Ringing, Machine.12228 

— Manual.12227 

Rises, Limiting Observable Tempera¬ 
ture.1009 

Room, Operating.12225 

Root-Mean-Square.3218 

-Values.3608 

Rope-Lay Cable.9009 

Rotary Phase-Converter.4013 

Rotating Machinery, Electric, Classi¬ 
fication. 4000 

— Machines, Forced Draft, Ambient 

Temperature.4300 (a) 

— Machines, Losses in.Table 402 

Rotor-Excited Commutator Motor. . . .4068 
Rotor Phase-Wound, of Induction 

Motor, Test Voltage.4361 (c) 

— Polyphase Induction-Motor, I 2 R 

Loss. 4336 ( b) 

Round Conductor.,.9018 

Rubber Insulated Wires and Cables, 

Thickness of Insulation.9405 

Rubber, Insulation, Hevea, Test Volt¬ 
age.9312 (c) ( d ) 


--N. E. Code, Test Voltage. .9312 ( b) 










































































































INDEX 


167 


SECTION 

s 


Saturation Factor. .4085 

— Percentage.4086 

Scattering Surfaces and Media.11022 

Scope of Rules for Transformer Con¬ 
nections.6402 

— of the 1921 Revision.Page iv 

Secondary Burden.8031 

— Winding.6020, 6021 

Section of Switches.12277 

— Relay Coil.12260 

— Switchboard.12224 

Sector Cable.9017 

Selectivity.13047 

— Average. 13048 

— Directional.13045 

— Radio-Frequency. 13049 

Selector.12504 

— Final.12275 

— Switch.12274 

Self-Impedance..12053 

— Ventilated Machine. 4046 

Semi-Automatic Telephone System. .12202 

— -Enclosed Machine.4043 

— -Mechanical Telephone System. . .12202 

Sending-End Impedance.2055 

Separately Ventilated Machine.4045 

Series Field Coils, Dielectric Tests.4361 ( b) 

— Loaded Line.4090, 6051 

— Transformer.8030 

“Set Up, To”.12236 

Shade.11049 

Short Circuit, Protection against. . . .2120 

-Stresses.2120 

— Time Rating.2221 

-— Standard Periods.2223 

— — Tests, Conditions for.2223 Note 

Shunt, Temperature Limits.8101 

-Rise.8204 

— -Loaded Line.12023 

— Switchboard, Marking of.8503 

Shut-Down, Correction to Time of. . . . . 2316 
-Duration of Tem¬ 
perature Test and.1015 

Side Circuit.12005 

— Negative.12220 

— Positive.'...12220 

— Ring.12219 

— Tip.12219 

Signal, Alarm.12292 

— Tell-Tale. 12291 

— Supervisory.12290 

Signaling, Automatic.12270 

— Harmonic Selective.12231 

— Multiple Harmonic.12232 

— Non-Multiple Harmonic.12233 

Simple Alternating Current. . .3214 

— Cross-Span Systems.5007 ( b) 

Simplex Circuit.12010 

Simplexed Circuit. ..12007 

Sine Wave..3212 


SECTION 

Sine Wave as Standardl200, 2332 (c), 2340 


-Deviation from.4351 

Single-Phase Circuit.. ..3324 

-Commutator Motor.4061 

Sinusoidal Current.3214 

Six-Phase Circuit.3320 

-Leads, Marking.6417 

— —• Windings and Three Phase 

Windings, Relation between . 6418 

Sleet-Proof.7043 

Slip Rings, Temperatures of. . .2116, 4106 
Slow Acting Relay.12287 

— Operating Relay.12255 

— Release Relay.12256 

Smooth Line.12016 

Sources, Luminous.11047 

Spark Condenser.12514 

Spark- Frequency.13019 

— Gap with Machines of High Capac¬ 

itance. 2361 

— Gap with Machines of Low Capac¬ 

itance . 2360 

— Gap Measurements.2359, 2363 (a) 

-Needle. 2364 

-Range of Voltage.2363 ( b) 

— — Sphere.2366 

— Gaps in Dielectric Tests, Use of. . .2359 

Sparking Distance, Needle Gap.2365 

— — Sphere Gap.2368 

Special Cases, Temperature Limits in. 1012 

— Temperature Limits.1007, 2232 

— and Specific Cases, General Com¬ 

ments on.....1010 

Specific Consumption.11045 

— Output of Lamps.11043 

Speed, Rated, of Electric Locomotives 5214 

— Regulation of Machines.3535 

-Test.2390 

Speeds, Above Rated.4250 (a) ( b ) 

Sphere Gap, Conditions for Test.2371 Note 
-Correction Factor for Air 

Density.2369, 2370 

— Spark Gap.2366 

Spherical Reduction Factor.11066 

Spherometer.2367 

Splash-Proof.7040 

Split Conductor.9019 

Spring, Armature.12264 

— Back Contact.12268 

— Contact.12262 

— Front Contact.12269 

— Impulse.12266 

— Make-Before-Break Contact 

(M. B. B.).12267 

— Main Contact.12263 

— Plunger.12265 

— Tension.12261 

Squirrel-Cage Windings, Temper¬ 
ature.2116, 4105 

Stability, Limitations of.4252 

Stalling Torque of Motors.4250 ( c ) 







































































































168 


INDEX 


SECTION 

Stand Test Temperatures, Railway- 

Motors.Table 802 

Standard, Annealed Copper.9050 

Standard Cable.12059 

— Duration of Equivalent Tests. . . . 2223 

— Resonance Curve.13028 

— Temperature for Institute Rating. .2205 

— Test Voltage.2356, 6356 

-, Apparatus Rated at 600 

Volts or less.7323 (a) 

-Voltage, Apparatus Rated 

Above 600 volts.7323 ( b ) 

-Auto-Transformers for 

Motor Starters.7323 (c) 

Standard, Working, Observable Tem¬ 
perature Rise the.1014 

Standards, Other Approved.Page v 

Star Connection, Transformers in. 

Test Voltage.6360 

Station, Pay.12213 

— Subscriber.12212 

— Toll.12214 

Stationary Induction Apparatus.... 6000 
-, Other Than Transformers, 

Rating.6223 

Stator-Excited Commutator Motor..4065 
Stators of Machines, Method of Tem¬ 
perature Measurement.4321 

Steam Engines, Fluctuation of.14001 

-Regulation of.14000 

— Turbines, Fluctuation of.14001 

-Regulation of.14000 

Storage Batteries.Page 105 

Strand.9003 

— Concentric.9007 

Stranded Conductor.9002 

— Wire.9005 

Stranding, Apparatus Cable.9402 

— Bunched.9402 

— Flexible.9402 

— Rope.9402 

— Rope-Lay, Symbol for.9402 

— Standard.9400, 9401 

Stray Load Losses.4335 Note 

-Induction Machines.4342 ( b) 

-Synchronous Machines. 4342 (a) 

Street, Railways, Standard Height of 

Trolley Wires.5601 

Submersible.7041 

Subscriber Line.12215 

-Circuit.12216 

— Set (“Subset”).12211 

— Station (“Substation”).12212 

Substation.5032 

— Machines and Transformers, Rail¬ 

way, Nominal Rating.5201 

— Machines and Transformers, Rail¬ 

way, Temperature Limits of. . . .5120 

Superposed Circuit.12003 

Superimposed Ringing Current.12229 

Supervisory Signal.12290 


SECTION 

Supporting System for Trolley 

Wires.5007 (a) 

Switch.7001 

— Automatic.12271 

— Auxiliary.7004 

— Connector.12275 

— Control.7003 

— Dielectric Tests.6361 ( g ), 8311 

— Finder.12272 

— Frame.12276 

— Heat Tests.7301 

— Line.12273 

— Master.7002 

— Rating.4201, 7201 

— Selector.12274 

— Temperature Limits...7101 

— Tests of.7323 

Surges, Continuous.7373 

Susceptance, Symbol.3604 

Susceptibility.3604 

Suspension, Catenary, for Trolley.5006 ( c ) 

— Direct for Trolley.5006 (b) 

— Messenger for Trolley.5006 (c) 

Sustained Radiation.13029 

Switchboard.12223 

— Section.12224 

Switching and Control Apparatus.7000 

-Phase-Failure Protec¬ 
tion.7023 

-Phase-Reversal Protec¬ 
tion. 7024 

— —-Under-Voltage Protec¬ 

tion. ...7022 

-Under-Voltage Release. 7021 

Switches, Section of.12277 

Switchroom.12278 

Symbols and Abbreviations.3604 

— for Maximum, Instantaneous and 

R. M. S. Values.3608 

— Photometric.11067 

Symmetrical Polyphase System.3348 

— Voltages and Currents.3344 

Synchronism Indicator.8005 

Synchronoscope.8005 

Synchronous Commutating Machines.4018 

— Condenser.4015 

— Converter.4010 

- I*R Loss.4336 (c) 

— Machine.4019 

— Machine, Core Losses.4339 ( b ) 

-Stray Load Losses.4342 (a) 

— Motor.4023 

— Phase Advancer. . -..4015 

— System.12508 

Synchroscope.8005 

System, Bracket.5007 ( d) 

— Bridge.5007 ( e) 

— Cross-Span Messenger.5007 (c) 

-Simple.5007 (6) 

— Distribution.5031 

— Efficiency.2332 Note, 353^ 

— Messenger Cross-Span.5007 (d) 




































































































INDEX 


169 


SECTION 

System Simple Cross-Span.5007 (ft) 

— Supporting, for Trolley Wires. .5007 (a) 

— Synchronous.12508 

— Telephone, Automatic.12201 

-Manual.12200 

-Semi-Automatic.12202 

-— -Mechanical.12202 

— Transmission.5030 

T 

“T” Equivalent Circuit.12103 

Table of Contents.Page vii 

Tables of Copper Wire.9203 

Tap Leads.6412, 6419 

Telegraph Cables, Test Voltage_9312 (/) 

Telephone Cables, Test Voltage. . 9312 (/) 

— Exchange.12203 

— •— Area or District. ( .12204 

— Impulse Repeater.12289 

— Interference Factor.3278, 4352 

— Receiver.12300 

— Repeater.12294 

— System, Automatic.12201 

-Manual.;.12200 

-Semi-Automatic.12202 

--Mechanical.12202 

— Traffic.12241 

— Transmitter. : .12302 

Tell-Tale Signal.12291 

Temperature, Ambient.3000 

-by Idle Unit..2300 (c) 

— — for Testing.2310 

-Forced Draft Machines. . .4300 (a) 

-Measurement of.2300 (a) ( ft) 

— — Meters.8201 

-Shunts.8201 

— Coefficient of Copper.2321 

-of Standard Annealed Cop¬ 
per.9050 ( d) 

— Correction for Air-Blast Trans¬ 

formers.6311 

-for Cooling after Shut 

Down.6320 (c) 

— Detectors, Location of.2323 

— Limiting “Hottest-Spot”.1005 

— — Observable.1006 

-of Oil.1007 

-of Shunts.8101 

— Limits, Enclosed Machines.4319, 4320 

-for Low Ambients.4110 

-in Special Cases, Comments on. 1012 

— Maximum, of Wires or Cables. . . .9100 

— Measurement of Low Resistance 

Circuit.2322 

— Measurements, Methods of. .1001, 1002 

— — during Heat Run.2315 

— Measurement, Embedded De¬ 

tector Method.2323, 4321 


-Resistance Method. .2322, 6320 (c) 

-Method of, for Transformers. . .6320 

-Thermometer Method 

.2231 (ft), Table 100 


SECTION 

Temperature of Contactors.7102 

— — Parts other than Windings 
.2116, 4105 (d), 4106, 4107, 4108 

-Reference for Efficiency 

.1501, 1502, 2332 (d) 

-Reference for Meter and In¬ 
strument Characteristics.8301 

— of Transformer Winding... .6320 (a) (c) 

— Rise and Ultimate Temperature of 

Shunts .8101 (a) (ft), 8204 

— — for Any Ambient Temper¬ 

ature .2310, 8300 

-Limiting Observable, for 

Cotton, Silk, Paper, etc. 
when not Treated, Impreg¬ 
nated nor Immersed in Oil 
.2231 (a) 

— — Limiting Observable where 

Thermometers are Applied 
Directly to Bare Wind¬ 
ings.2231 (ft) 

-Limiting Observable for Com¬ 
mutators, Collector Rings, 

etc..2231 (c) 

-Limiting Observable for High 

Ambients. 2231 (d) 

-Maximum, in Service.4110 

-* Meter and Instrument Wind¬ 
ings .8203 

-Observable, the Working 

Standard.1014 

-Stand Test, of Railway Motors, 

.Table 502 

-Shunts.8204, 8300 

-with Ambient Less than Stand¬ 
ard.2211, 2212 

— Rises, Limiting Observable 

.1009, 2230, Table 200 

— Symbols and Abbreviation.3604 

— Test, Duration of.2312, 2313, 2314 

-— and Correction to Time 

of Shut Down.1015 

— Tests of Transformers.6317 

Temperatures and Temperature Rises 

Permissible.1005 Note 2 

— of Metallic Parts of Machines 

.2116, 1007 

— of Oil, Limiting Observable.. .2232, 6202 

— Permissible, in Mixed Insulations 

.1005, 2104 (6) 

— Permissible, with Insulations of 

More Than One Class.2104 

Tension Spring.12261 

Test Voltage, Apparatus Rated above 

600 Volts.7323 (ft) 

— — Apparatus Rated at 600 Volts 

or Lower.7323 (a) 

-Auto-transformers for Motor 

Starter. ..7323 (c) 

-Annunciator Wires and Cables 

.9312 (/) 

-Cables.9311 













































































170 


INDEX 


SECTION 

Test Voltage Conditions for 2350, 2351,2352 

-Distributing Transformers.6361 

-Duration of Application of.2355 

-for Machines. ..1301 

-Exceptions to Standard.4361 

— — Frequency and Wave Form 

.2354, 4358 

-Hevea Rubber Insulation 

..'. .9312 (c) (d) 

-Instrument Current Trans¬ 
formers. ....8311 

-Potential Transformers.8310 

— — Measurement of.2359, 2368 

-Meters and Instruments.8312 

— — Rubber Insulation.9312 (6) 

-Standard.2356, 6356 

— — Values of, and Exceptions 

...2356, 6363, 8312 

— — Telegraph and Telephone 

Cables. .9312 ( b) 

— — Varnished Cambric and Im¬ 

pregnated Paper.9312 ( e) 

-Wires and Cables.9312,9313 

Testing of Cables, Immersion in 

Water.9301 (a) (6) 

Thermal Capacity.5502 Note 

Thermometer, Covering of.. .2320, 6320 ( d) 
Thermometer Method of Measuring 

Temperature.Table 100, 2231 (£>) 

— Pads and Putty.2320, 6320 (d) 

Thickness of Insulation for Rubber 

Insulated Wires and Cables. 9405 

Third Rail.5003 (c) 

-Elevation of...5003 (g) 

-Gage of.5003 (/) 

— — Protection.5003 ( h) 

-Standard Elevation of.5603 (a) 

-Gage of.5602 

Three-Phase Circuit. 3326 

-Transformers, Marking Leads 

of. 6410 

-Transformers, Rules Applicable 

to. 6416 

-Winding and Six Phase, Rela¬ 
tion between.6418 

Time Lag, Error due to.2301 

Tip Side, or Tip Wire.12219 

‘‘To Call”.12234 

‘‘To Clear”. 12246 

‘‘To Dial”.12235 

“To Disconnect”. 12245 

“To Make Busy”. .. 12244 

‘‘To Release”..;;....12245 

“To Set Up”. 12236 

Toll Central Office...12206 

— Station.12214 

Totally Enclosed Machine.4044 

Torque of Meters and Instruments. .. .8501 

— Stalling, of Motors.4250 (c) 

Tractive Effort, Continuous.5213 

— — Nominal. .5212 

Traffic, Telephone. 12241 


SECTION 

Transformer.6001 

— Air-Blast, Temperature Measure¬ 

ment.6320 (6) 

— A-C. Connected to Permanently 

Grounded Single-Phase Systems, 

Test Voltage.6320 (c) 

— Angular Displacement.6412 ( b ) 

— -between.6411 ( b ) 6418 (6) 

— Coefficient of Coupling.12302 

— Commutator Motor.4072 

— Conduction Commutator Motor. . . 4073 

— Connections..6402 

— Constant-Potential, Rated Current.6031 

-Primary Current.6031 

-Regulation of.6053 

— Current Ratio.6035, 8033 

— Diagrammatic Sketch of Connec¬ 

tions.6404 

— Distributing Test Voltages.6361 (a) 

— Expression of Rating.4221,6221 

— Graded Insulation.6363 

— High-Voltage Winding.6020,6021 

— Instrument.8030 

-on Closed Secondary Circuit... .8112 

-— Open Secondary Circuit.8111 

— Low-Voltage Winding.6020,6021 

— Load Losses. 6337 

— Loading for Temperature Tests... .6317 

— Losses of....6334, 6335 

— M arked Ratio.8034 

— Marking of Leads.6403 to 6419 

— Method of Temperature Measure¬ 

ment.. 6320 

— No-Load Losses.6336 

— Oil Immersed, Temperature Meas¬ 

urement..6320 (c) 

— On Circuits of 25 Volts or Lower, 

Test Voltage.6361 (d) 

— On Star Connected Three-Phase 

Systems, Test Voltage.6361 (/) 

— Per Cent Drop.6050 Note 

— Primary Winding.6020,6021 

— Ratio of.6033, 8034 

— Rating of.6221 

— Reactance Drop.6391 (a) ( b) 

— Regulation of.6391 

— Relation between Three-Phase and 

Six-Phase Windings.6418 ( b) 

— Secondary Winding.6020, 6021 

— Single-Phase, Location of Hi Lead. 6408 

— Single Phase, Parallel Operation... .6409 

-Polarity. 6407 

-Order of Numbering Leads 

in any Winding...6405 

— Single-Phase Relation of Order of 

Numbering Leads of Different 
Windings.6406 

— Six-Phase, Markings of Leads.6417 

— Star Connection, Test Voltage.6360 

— Stray Load Losses. .6337 

— Temperature Correction for Cool¬ 

ing After Shut-Down.6320 (c) 




























































































INDEX 


171 


SECTION 

Transformer Temperature Measure 

ments of.. 6320 (a) ( c ) 

— Test Voltage.. .8310, 8311 

— Testing by Induced Voltage.6362 

— Three-Phase, Interphase Connec¬ 

tions Made Outside of Case. . .6311 

-Location of Hi Lead. 6415 

-Marking of Full Winding 

Leads.6410 

-— Method of Loading.6317 (c) 

-— Parallel Operation.6414 

— — — Relation between High and 

Low - Voltage Windings 
.6411 (a) 

— — — Tap Leads.6412 to 6419 

— -to Six-Phase.6416 

— Turn Ratio,.6033 

— Using Class A Insulation, Limiting 

Observable Temperatures and 
Temperature Rises.6201 

— Voltage Ratio,.6034, 8032 

— Volt-Ampere Ratio.6036 

— Water-Cooled, Ambient of.6300 

— Water-Cooled, Temperature.6015 

— Windings.6001 

— — Grounded Voltage Tests.6362 

— with Graded Insulation.6362 

Transmission Factor.11025 

— Lines, Regulation of.15000 

— System. 5030 

Transmitter, Telephone.12302 

— (Telegraphy).12507 

Triplex Cable.9015 

Trolley, Classes of Suspension. . . .5006 (a) 

— Direct Suspension.5006 (6) 

— Messenger or Catenary Suspension 

.5006 (c) 

— over Steam Railroad Tracks.5601 

— Supporting Systems.5007 

— Wire.. • • • 5004 

-Height, Standard.5601 

Trunk.12247 

— Circuit.12248 

Trunked Call.12249 

Tuning.13030 

Turbine, Hydraulic, Regulation of. . . . 14002 

— Steam, Fluctuation of.14001 

-Regulation of.14000 

Twin Cable.9013 

— Wire.9014 

Twisted Pair. 9016 

Two-Phase Circuit.3328 

Two-Wire Circuit.12002 

u 


U Equivalent Circuit.12105 

Underground Contact Rail.5003 ( e ) 

Under-Voltage or Low Voltage Pro¬ 
tection .7022 

—-Release.7021 

Unidirectional Illumination.11030 

Unipolar Machine.‘.4028 

Unit, Generator, Regulation of.14003 


SECTION 

Units in Which Rating Shall be Ex¬ 
pressed .4220 to 4223, 6221, 6223 


— Photometric. .11067 

Utilization, Coefficient of.11033 

V 


Values, Minimum, of Insulation Re¬ 
sistance .2382 

Variation Factor.“. . . . 11034 

— in Alternators.-. 4088 

-Prime Movers.14010 

— Range in Illumination.11035 

Varnished Cambric Insulation, Test 

Voltage.9312 ( e) 

— — — Working Temperature 

...9100, 9202 Note 

Varying Field Commutator Motor.4068 

— Speed Motor ..4039 

Vector Diagram. .3230 

Vector Phase.. .3222, 3228 

— Quantities,Representation in Print.3608 

— Representation and Angular Velo¬ 

city.3228 

Velocity, Angular. . . ..3228 

— of Rotation, Symbol and Abbrevia¬ 

tion. 3604 


Ventilated Motor, Rise Compared to 


Stand Test.5502 

Ventilating Blower Losses.4343 ( b ) 

Virtual. 3218 

Visibility. 11002 

Voltage, Induced, Testing Trans¬ 
formers by.6362 


— Measurement for Dielectric Tests 


.2359 to 2369 

— — in Dielectric Tests of Machines.2359 


— Ratio of Transformer.6034, 8032 

— Regulation.2390 (c), 3535 

— Regulator.6011 

-Contact.6012 

— — Induction.6013 

— — Magneto.6014 

— Standard Test.2356, 6356 

— Symbols.. ! .3604 

— Symmetrical.3348 

— Test, for Dielectric Strength 

Tests.1301 

— Tests, Conditions for.2350 to 2352 

-for Machines. . . . 1301, 2350 to 2357, 

4358, 4361, 6360 to 6362, 8311, 8312 

— Transformer.8030 

-Tests.2356, 8310 

Volt-ampere.3238 

— Ratio of Transformer.6036 

— Reactive.3246 

Voltmeter, Crest.".8004 

— Measurements.2362 


Voltmeters in Dielectric Tests, Use of. .2359 
Volume Resistivity.9050, 9202 


w 


Water-Cooled Machine.4047 






























































































172 


INDEX 


SECTION 

Water Cooled Machinery, Ambient 

Temperature of Reference for 2212 

Water-Cooled Transformer.6300 

-Ambient Temperature.6300 

-Temperature of.6105 

Watthour Meter.8002 

W attmeter.8003 

Wave, Crest-Factor of.3266 

— Deviation Factor.3274,4351 

— Distortion Factor.3274,4351 

— Electromagnetic.13015 

— Equivalent Sine.3260 

— Form.(See Wave Shape) 

-Factor.3270 

— Length Constant.12058 

-Meter.13035 

— Meter.13035 

— Shape.1200, 2332, (c) 2340, 3212 

-and Efficiency.2332 (c) 

— — of Test Voltage of Machines. .2354 

— Sine. 3214 

-as Standard_1200, 2332 (c) 2340 

— -— Deviation from.4351 


Weatherproof Cable Stranding. .9400, 9401 

Weight on Drivers.. . .5211 

Windage and Bearing Friction Losses. . 4337 


SECTION 

Windage, Railway Motors.5338, 5339 

Winding, High-Voltage and Low- 

Voltage.6020 

— Primary and Secondary.6021 

Windings, High and Low-Voltage, 

Relation between.6411 

— Meter and Instrument, Tempera¬ 

ture Rise.8203 

Wire.9000 

— Copper, Tables of.9203 

— Designation by Diameter or Gage 

Numbers.9200 

— Gages.9200, 9201 

— Half Sizes.9402 Note 

— (or Cable), Messenger.5005 

— Negative.12220 

— Positive.12220 

— Ring.12219 

— Stranded.9005 

— Tip. 12219 

— Trolley.5004 

-Standard Height.5601 

— Twin.9014 

Wires and Cables, Rubber Insulated, 

Thickness of Insulation.9405 

Wires, Bank.12279 















































4 










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